Method of fabricating a semiconductor multi-package module having inverted land grid array (lga) package stacked over ball grid array (bga) package

ABSTRACT

A method is provided for making a semiconductor multi-package module, by providing a lower molded ball grid array package including a lower substrate and a die, affixing an upper molded package including an upper substrate in inverted orientation onto the upper surface of the lower package, and forming z-interconnects between the upper and lower substrates.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.11/626,272 filed Jan. 23, 2007, which is a continuation of U.S.application Ser. No. 11/374,378, now U.S. Pat. No. 7,169,642, which is aDivision of U.S. application Ser. No. 10/681,735, now U.S. Pat. No.7,057,269. U.S. application Ser. No. 10/681,735 claims the benefit ofU.S. Provisional Application No. 60/417,277. U.S. application Ser. No.11/374,378 also is a Continuation-in-Part of U.S. application Ser. No.10/618,933, now U.S. Pat. No. 7,034,387. U.S. application Ser. No.10/618,933 claims the benefit of U.S. Provisional Application No.60/460,541.

This application is related to U.S. application Ser. No. 10/681,572, nowU.S. Pat. No. 7,061,088, U.S. application Ser. No. 10/681,833, now U.S.Pat. No. 6,933,598, U.S. application Ser. No. 10/681,583, now U.S. Pat.No. 7,045,887, U.S. application Ser. No. 10/681,747, now U.S. Pat. No.6,906,416, U.S. application Ser. No. 10/681,584, now U.S. Pat. No.7,049,691, and U.S. application Ser. No. 10/681,734, now U.S. Pat. No.7,053,477.

BACKGROUND

This invention relates to semiconductor packaging.

Portable electronic products such as mobile phones, mobile computing,and various consumer products require higher semiconductor functionalityand performance in a limited footprint and minimal thickness and weightat the lowest cost. This has driven the industry to increase integrationon the individual semiconductor chips.

More recently the industry has begun implementing integration on the“z-axis,” that is, by stacking chips, and stacks of up to five chips inone package have been used. This provides a dense chip structure havingthe footprint of a one-chip package, in the range of 5×5 mm to 40×40 mm,and obtaining thicknesses that have been continuously decreasing from2.3 mm to 0.5 mm. The cost of a stacked die package is onlyincrementally higher than the cost of a single die package and theassembly yields are high enough to assure a competitive final cost ascompared to packaging the die in individual packages.

The primary practical limitation to the number of chips that can bestacked in a stacked die package is the low final test yield of thestacked-die package. It is inevitable that some of the die in thepackage will be defective to some extent, and therefore the finalpackage test yield will be the product of the individual die testyields, each of which is always less than 100%. This can be particularlya problem even if only two die are stacked in a package but one of themhas low yield because of design complexity or technology.

Another limitation is the low power dissipation of the package. The heatis transmitted from one die to the other and there is no significantdissipation path other than through the solder ball to the motherboard.

A further limitation is electromagnetic interference between the stackeddie, particularly between RF and digital die, because there is noelectrical shielding of either die.

Another approach to integrating on the “z-axis” is to stack die packagesto form a multi-package module. Stacked packages can provide numerousadvantages as compared to stacked-die packages.

For instance, each package with its die can be electrically tested, andrejected unless it shows satisfactory performance, before the packagesare stacked. As a result the final stacked multi-package module yieldsare maximized.

More efficient cooling can be provided in stacked packages, by insertinga heat spreader between the packages in the stack as well as at the topof the module.

Package stacking allows electromagnetic shielding of the RF die andavoids interference with other die in the module.

Each die or more than one die can be packaged in a respective package inthe stack using the most efficient first level interconnect technologyfor the chip type and configuration, such as wire bonding or flip chip,to maximize performance and minimize cost.

The z-interconnect between packages in a stacked multi-package module isa critical technology from the standpoint of manufacturability, designflexibility and cost. Z-interconnects that have been proposed includeperipheral solder ball connection, and flexible substrate folded overthe top of the bottom package. The use of peripheral solder balls forz-interconnects in stacked multi-package modules limits the number ofconnections that can be made and limits design flexibility, and resultsin a thicker and higher cost package. Although the use of a flexiblefolding substrate provides in principle for design flexibility, there isno established manufacturing infrastructure for the folding process.Moreover, the use of a flexible folding substrate requires a two metallayer flex substrate, and these are expensive. Furthermore the foldedflexible substrate approach is restricted to low pincount applicationsbecause of limits in routing the circuitry in two metal layersubstrates.

The various z-interconnect structures are described in further detailwith reference to FIGS. 1A, 1B and 2-4.

FIG. 1A is a diagrammatic sketch in a sectional view illustrating thestructure of a standard Ball Grid Array (“BGA”) package, wellestablished in the industry, that can be used as a bottom package in astacked multi-package module (“MPM”). The BGA, shown generally at 10,includes a die 14 attached onto a substrate 12 having at least one metallayer. Any of various substrate types may be used, including forexample: a laminate with 2-6 metal layers, or a build up substrate with4-8 metal layers, or a flexible polyimide tape with 1-2 metal layers, ora ceramic multilayer substrate. The substrate 12 shown by way of examplein FIG. 1A has two metal layers 121, 123, each patterned to provideappropriate circuitry and connected by way of vias 122. The die isconventionally attached to a surface of the substrate using an adhesive,typically referred to as the die attach epoxy, shown at 13 in FIG. 1Aand, in the configuration in FIG. 1A, the surface of the substrate ontowhich the die is attached may be referred to as the “upper” surface, andthe metal layer on that surface may be referred to as the “upper” metallayer, although the die attach surface need not have any particularorientation in use.

In the BGA of FIG. 1A the die is wire bonded onto wire bond sites on theupper metal layer of the substrate to establish electrical connections.The die 14 and the wire bonds 16 are encapsulated with a moldingcompound 17 that provides protection from ambient and from mechanicalstress to facilitate handling operations, and provides a surface formarking for identification. Solder balls 18 are reflowed onto bondingpads on the lower metal layer of the substrate to provideinterconnection to the motherboard (not shown in the FIGS.) of a finalproduct, such as a computer. Solder masks 125, 127 are patterned overthe metal layers 121, 123 to expose the underlying metal at bondingsites for electrical connection, for example the wire bond sites andbonding pads for bonding the wire bonds 16 and solder balls 18.

FIG. 1B is a diagrammatic sketch in a sectional view illustrating thestructure of a BGA, generally similar to the BGA 11 shown in FIG. 1A,except that here the molding 117 completely covers the substrate as wellas the die and wire bonds. The molding configuration of FIG. 1B isformed by applying the molding compound over an array of a number ofBGAs, curing the molding, and then separating the encapsulated packages,for example by saw singulation. Typically the molding in such a packagehas vertical walls at the edges of the package. In such a package,unlike a BGA as in FIG. 1A, no marginal portion of the upper surface ofthe substrate 12 is exposed and, accordingly, no electrical traces areexposed on the upper surface of the substrate. Many smaller packagescurrently are saw-singulated packages, often referred to as “chip scalepackages.”

FIG. 2 is a diagrammatic sketch in a sectional view illustrating thestructure of an example of a 2-stack MPM, generally at 20, in which thez-interconnect is made by way of solder balls. In this MPM a firstpackage (which may be referred to as the “bottom” package) is similar toa standard BGA as shown in FIG. 1A (and similar reference numerals areemployed to point to similar features of the bottom package in FIGS. 1Aand 2). A second package (which may be referred to as the “top” package)is stacked on the bottom package and is similar in structure to thepackage of FIG. 1B (and similar reference numerals are employed to pointto similar features of the top package in FIGS. 1B and 2), except thatthe solder balls in the top package are arranged at the periphery of thetop package substrate, so that they effect the z-interconnect withoutinterference with the encapsulation of the bottom BGA. Particularly, thetop package in FIG. 2 includes a die 24 attached onto a substrate 22having at least one metal layer. The top package substrate 22 shown byway of example in FIG. 2 has two metal layers 221, 223, each patternedto provide appropriate circuitry and connected by way of vias 222. Thedie is conventionally attached to a surface of the substrate (the“upper” surface) using an adhesive, typically referred to as the dieattach epoxy, shown at 23 in FIG. 2.

In the top package in the MPM of FIG. 2, as in the bottom package, thedie is wire bonded onto wire bond sites on the upper metal layer of thesubstrate to establish electrical connections. The top package die 24and wire bonds 26 are encapsulated with a top package molding compound27. Solder balls 28 are reflowed onto bonding pads located on theperipheral margin of the lower metal layer of the top package substrateto provide z-interconnection to the bottom package. Solder masks 225,227 are patterned over the metal layers 221, 223 to expose theunderlying metal at bonding sites for electrical connection, for examplethe wire bond sites and bonding pads for bonding the wire bonds 26 andsolder balls 28.

The z-interconnection in the MPM of FIG. 2 is achieved by reflowing thesolder balls 28 attached to peripheral bonding pads on the lower metallayer of the top package substrate onto peripheral bonding pads on theupper metal layer of the bottom BGA. This type of z-interconnectrequires that the upper and lower substrates be designed with matchingpads for the interconnect balls. If one of the packages is exchanged forone in which the substrate has a different pad arrangement (differentsize or different design), then the substrate for the other package mustbe reconfigured accordingly. This leads to increased cost formanufacture of the MPM. In this configuration the distance h between thetop and bottom packages must be at least as great as the encapsulationheight of the bottom package, which may be 0.25 mm or more, andtypically is in a range between 0.5 mm and 1.5 mm. The solder balls 28must accordingly be of a sufficiently large diameter that when they arereflowed they make good contact with the bonding pads of the bottom BGA;that is, the solder ball 28 diameter must be greater than theencapsulation height. A larger ball diameter dictates a larger ballpitch that in turn limits the number of balls that can be fitted in theavailable space. Furthermore the peripheral arrangement of the solderballs forces the bottom BGA to be significantly larger than the mold capof a standard BGA. Furthermore the peripheral arrangement of the solderballs increases the overall package size (the size increases accordingto the number of ball rows and the ball pitch). In small BGAs, usuallyreferred to as Chip Scale Packages (“CSP”), the package body size is 1.7mm larger than the die. In standard BGAs the body size can be as much asabout 2-3 mm larger than the mold cap. Moreover, the top package in sucha configuration must be made of comparable size to the bottom one eventhough it may contain a small chip with many fewer interconnects. Inthis configuration the top package substrate must have at least 2 metallayers to facilitate the electrical connections.

FIG. 3 is a diagrammatic sketch in a sectional view illustrating thestructure of an example of a known 2-stack flip chip MPM, showngenerally at 30. In this configuration the bottom BGA flip chip packageincludes a substrate 32 having a patterned metal layer 31 onto which thedie 34 is connected by flip chip bumps 36, such as solder bumps, goldstud bumps or anisotropically conducting film or paste. The flip chipbumps are affixed to a patterned array of bump pads on the activesurface of the die and, as the active surface of the die faces downwardin relation to an upward-facing patterned metal layer of the substrate,such an arrangement may be referred to as a “die down” flip chippackage. A polymer underfill 33 between die and substrate providesprotection from ambient and adds mechanical integrity to the structure.Such a flip chip package, in which the substrate has a metal layer ononly the upper surface, is connected to the underlying circuitry (suchas a motherboard, not shown in the FIG.) by solder balls 38 connected tothe metal layer through solder vias 35.

The top BGA in this configuration is similar to the bottom BGA, exceptthat the top BGA has z-interconnect solder balls 338 connected (throughsolder vias 335 in the top substrate) to the metal layer 331 only at theperiphery of the top substrate. Solder balls 338 are reflowed onto themetal layer 31 of the bottom substrate to provide the z-interconnect.Particularly, the top BGA in this configuration includes a substrate 332having a patterned metal layer 331 onto which the top BGA die 334 isconnected by flip chip bumps 336. Between the top BGA die and substrateis a polymer underfill 333. A structure as in FIG. 3 is more appropriatefor high electrical performance applications, but it has similarlimitations to configurations of the type shown in of FIG. 2. Itpresents an improvement over the FIG. 2 configuration in that the bottomBGA has no molding, allowing for use of smaller diameter (h) solderballs at the periphery of the top BGA for connection between thepackages.

Particularly, this structure is more appropriate, for example, formodules containing stacks of identical memory chips having the sameconnections at the same locations to facilitate the z-interconnect. Itis not appropriate for stacking packages that have different chips withconnection points not located over one another in the stack. As in theconfiguration of FIG. 2, the peripheral arrangement of solder ballslimits the number of interconnects. Moreover, the packages mustnecessarily be of comparable size, and where the chip in one package issmaller than that in the other, the package having the smaller chip willbe forced to a larger size, imposing a higher cost.

FIG. 4 is a diagrammatic sketch in a sectional view illustrating thestructure of an example of a known 2-stack folded flexible substrateMPM, shown generally at 40. The bottom package in the configuration ofFIG. 4 has a 2-metal layer flexible substrate onto which the die isbonded via small beams to the first metal layer of the substrate. Thesecond metal layer of the bottom package substrate carries the solderballs for connection to the underlying circuitry, such as a motherboard(not shown). The substrate is large enough to be folded over the top ofthe package, thus bringing the electrical interconnect lines upwardwhere they are available for connection to the top package (an exampleof which is described below) by way of an array of solder balls on thetop package. The space around the die and between the die andfolded-over substrate is encapsulated 47 to provide protection andrigidity.

Referring to FIG. 4, the two-metal layer bottom package substrate 42includes a first metal layer 141 and a second metal layer 143, eachpatterned to provide appropriate circuitry and connected by way of vias142. A part of the first metal layer, over a part of the bottomsubstrate, is processed (for example, using an array of punches) topresent an array of cantilever beams or tabs 46 arranged to correspondto an array of interconnect pads on the active surface of the bottompackage die 44. Over this part of the substrate 42, which may bereferred to as the “die attach part”, the first metal layer 141 facesupwardly. The die is aligned, active surface downward, over the dieattach part of the substrate, and the cantilevers and the correspondinginterconnect pads are joined, typically for example by a “thermosonic”process employing a combination of pressure, heat, and ultrasonic energyto complete the electrical connections. The die 44 is affixed using anadhesive 43, typically a die attach epoxy, onto the die attach part ofthe flexible substrate 42. A second metal layer 143 of the bottompackage substrate 42 faces downwardly in the die attach part of thesubstrate. Solder balls 48 are reflowed onto bonding pads located on anarray on the downward-facing part of the second metal layer 143 toprovide for interconnection of the MPM to underlying circuitry (notshown). A solder mask 147 is patterned over the second metal layer 143to expose the underlying metal as bonding sites for electricalconnection, including the bond pads for connection with the underlyingcircuitry by way of solder balls 48, and the bond pads for connectionwith the top package by way of solder balls 18, as described below.

Another part of the bottom package substrate 42, extending adjacent thedie-attach portion, is folded up and over the bottom package die 44. Onthis folded-over portion of the flexible substrate 42 the first metallayer 143 faces upwardly. In the configuration of FIG. 4 the top packageis generally similar to the BGA of FIG. 1, in which the die is wirebonded onto wire bond sites on the upper metal layer of the substrate toestablish electrical connections. Particularly, the top package die 14is attached onto a substrate 12 having (in this example) two metallayers 121, 123, each patterned to provide appropriate circuitry andconnected by way of vias 122. The die is conventionally attached to theupper surface of the top package substrate using an adhesive 13,typically a die attach epoxy. The die 14 and the wire bonds 16 areencapsulated with a molding compound 17 that provides protection fromambient and from mechanical stress to facilitate handling operations,and provides a surface for marking for identification. Solder balls 18are reflowed onto bonding pads 143 on the upward-facing metal layer ofthe folded-over bottom package substrate to provide z-interconnectionbetween the top and the bottom packages.

An advantage of a structure as in FIG. 4 is that the folded-oversubstrate provides sufficient area on the upward-facing surface of thefolded-over bottom package substrate to accommodate a full array ofsolder balls in the top package and to accommodate more complexinterconnect between the two packages. It also provides for a smallpackage footprint. A primary disadvantage of this configuration is thehigh cost of the substrate and the unavailability of folding technologyand equipment.

A lack of folding technology and equipment makes manufacture of the2-stack folded flexible substrate MPM configuration more complex andmore costly. The two substrates must be designed such that the padsmatch for the interconnect balls. If one of the packages is exchangedfor one in which the substrate has a different pad arrangement(different size or different design), then the substrate for the otherpackage must be reconfigured accordingly. This leads to increased costfor manufacture of the MPM. Moreover, all the interconnects from the topto the bottom package must be routed through the folded portion of theflex substrate at one edge of the package. This increases the routingdensity and increases the length of the routing traces, resulting inhigher inductance and lower electrical performance of the MPM.

A common feature of all these stacked package configurations is thatthey enable pretesting of each package, and provide for production MPMswith higher final test yields.

SUMMARY

This invention is directed to multi-package modules. According to theinvention, z-interconnection between the stacked packages in the MPM iswire bond based, and an upper package is inverted. Generally, theinvention features various configurations of various stacked packages,including a bottom (lower) package and at least one inverted top (upper)package, and methods for stacking and interconnecting the variouspackages by wire-bonding based z-interconnection.

In the multi-package module according to the invention the package stackcan include any of a variety of BGA and/or any of a variety of Land GridArray (“LGA”) packages and/or any of a variety of bump chip carrierpackages; the package stack can include wire bonded and/or flip chippackages; the package stack can include a thermal enhancement featureenabled by one or more heat spreaders in or on the stack; the packagestack can include one or more packages having a flip chip bonded diebonded either to the top or to the bottom of the BGA or LGA; the packagestack can include one or more BGA and/or LGA having more than one die inthe package stacked or side by side; the stack can includeelectromagnetic shield for one or more of the packages; and the stackcan include any substrate, laminate or build-up or flexible or ceramic,provided that the z-interconnect pads are made available for bonding onthe periphery of the packages.

In one general aspect the invention features a multi-package modulehaving stacked lower and upper packages, each package including a dieattached to a substrate, in which the upper package is inverted and theupper and lower substrates are interconnected by wire bonding.

The invention provides for excellent manufacturability, high designflexibility, and low cost to produce a stacked package module having alow profile and a small footprint. The wire bond z-interconnect is wellestablished in the industry; it is the lowest cost interconnecttechnique and it is directly applicable, without significantmodification, to the stacked multi-package modules of the invention. Itprovides design flexibility to the relative size of the BGA to LGA thatcan be bridged by wire length. Using available techniques and equipmentthe wire in a wire bond can be as short as 0.5 mm or as long as 5 mm.The arrangement of the z-interconnect pads can be implemented througheither or both BGA and LGA substrate designs. Moreover, using wire bondsaccording to the invention z-interconnect can be formed between padsthat are not precisely aligned over one another, by employing so-called“out of sequence bonding” that is in current use in the industry. Thewire bonding pitch is the finest available technology in the industry at50 microns currently, and projected to go to 25 microns. This is finerthan any other interconnect including flip chip (around 200 microns) orsolder balls (at about 500 microns), and therefore provides for moreinterconnects between packages (z-interconnects) in the same availablespace.

Wire bonding using a wire bonding machine provides design flexibilityfor interconnecting pads, because the connections are programmed in thewire bonder, avoiding the need for hard tooling substrates to match eachother and connect with solder balls. When the relative BGA and LGApackage sizes change, the wire bonding can be reconfigured toaccommodate the differences by program changes. If the top package mustbe smaller than the bottom, wire bonding can accommodate sizedifferences at least up to 9 mm. This allows for use of the smallestpackage needed to accommodate the chip size, and thus optimizes thetotal cost of the MPM.

Wire bonding can interconnect pads that are “out of sequence,” that is,not situated in the desired order and not precisely above each other ineither package, so long as they are not too far apart. Where necessary,the pads can be appropriately routed to a location close enough for wirebonding. This flexibility allows stacking of packages that do not havethe “desired” order or location of interconnect pads. As the chiptechnology advances usually the chip size shrinks and design variantsare developed with either more connections or some connections withdifferent order. The bonding flexibility provided by wire bonding allowsthe user to maintain the same package size but vary the substratedesign. This results in lower cost and faster time to market, bothcritical for new products.

The BGAs and LGAs, including chip scale packages, are standard in theindustry, providing the lowest cost and the widest availability. Thisprovides significant flexibility in selecting the packages to be stackedand, therefore, in the kinds of functions that can be integrated intothe MPM.

A typical BGA thickness is 1.0 mm and LGA thickness is 0.8 mm. Thestacking of an inverted LGA on top of a BGA according to the inventioncan be completed using an adhesive having a finished thickness in therange 10-50 microns. This structure provides for a lower profile MPMcompared to conventional constructs that employ solder balls for thez-interconnect. The footprint of the MPM according to the invention isdetermined by the maximum chip size of the stack. A typical minimumfootprint for the BGA or LGA is 1.7 mm larger than the die size. Thewire bond z-interconnect generally requires that the top LGA beminimally smaller than the bottom BGA, by about 0.1 mm to 0.8 mm, toaccommodate the wires without shorting to the substrate metal edges. Ifthe top package must be significantly smaller than the bottom package,wire bonding can accommodate size differences at least up to 9 mm. Thisallows for minimizing the size of the package needed to accommodate thechip size, and thus for optimizing the total cost of the MPM. Both thefootprint and the thickness of the stacked package MPM according to theinvention fall within accepted ranges for most applications.

In some embodiments the multi-package module includes three or morepackages, affixed serially to form a stack.

In one general aspect the invention features a multi-package modulehaving stacked first (“bottom”) and second (“top”) packages, the bottompackage being a BGA package and the top package being an LGA package,each package including a first die attached to a substrate, in which theLGA package substrate and the BGA package substrate are interconnectedby wire bonding, and in which the LGA package substrate is inverted sothat the LGA substrate surface to which its die is attached is downward.In some embodiments the second package is an LGA package, and in someembodiments the second package is a saw-singulated package, and may be achip scale package. In some embodiments the second package is a bumpchip carrier package.

In another aspect the invention features a multi-package module havingstacked first (“bottom”) and second (“top”) packages, the bottom packagebeing a BGA package and the top package being an inverted LGA package,in which the inverted LGA package substrate and the BGA packagesubstrate are interconnected by wire bonding, and in which at least oneof the packages is provided with a heat spreader. In some suchconfigurations a heat spreader may additionally be configured to serveas an electrical shield, particularly for example where the heatspreader is situated over a lower die, that is, between a bottom and atop package in the stack. In some embodiments the heat spreader isaffixed to the upward surface of a topmost LGA package, and in suchembodiments the heat spreader is exposed to ambient at the topmostsurface of the MPM.

In another aspect the invention features a multi-package module havingstacked first (“bottom”) and second (“top”) packages, the bottom packagebeing a flip-chip BGA package having a flip-chip in a “die-up”configuration and the top package being an inverted LGA package, inwhich the top substrate and the bottom package are interconnected bywire bonding. In some embodiments the top package is a stacked diepackage; in some embodiments the adjacent stacked die in the stacked diepackage can be separated by spacers. In some embodiments the die on theBGA package is at least partially enclosed within an electrical shield(a “can” or “cage) affixed to the under surface of the BGA substrate. Insome embodiments the bottom package substrate includes an embeddedground plane, the ground plane being configured to serve also for heatdissipation and as an electrical shield. In some embodiments a pluralityof inverted second (“top”) packages is affixed over a plurality of dieattach regions on the upper surface of the first (“bottom”) packagesubstrate.

In another aspect the invention features a multi-package module havingstacked first (“bottom”) and second (“top”) packages, the bottom packagebeing a flip-chip BGA package having a flip-chip in a “die-down”configuration and the top package being an inverted LGA package, inwhich the top substrate and the bottom package are interconnected bywire bonding. In some embodiments the flip-chip die on the bottompackage is provided with an electrical shield.

In another aspect the invention features a multi-package module havingstacked first (“bottom”) and second (“top”) packages, the bottom packagebeing a BGA package and the top package being an inverted LGA package,in which the inverted LGA package substrate and the BGA packagesubstrate are interconnected by wire bonding, and in which either thetop LGA package or the bottom BGA package is a stacked die package, thatis, the package includes a stack of two or more die connected to asurface of the substrate; or in which both packages are stacked diepackages.

In some such embodiments the top LGA package may include a stack of twoor more die affixed to, and connected (as for example by wire bonding)to the upside of the LGA substrate (oriented downward in the invertedLGA package).

In another aspect the invention features a multi-package module havingstacked bottom and top packages, the bottom package being a BGA packageand the top package being an inverted LGA package, in which anadditional die is attached to the bottom surface of the LGA substrate(oriented upward in the inverted LGA package), that is, on the LGAsubstrate surface opposite the surface to which a first die is attached.In such embodiments there is at least one die on both the upper and thelower (downward and upward) surfaces of the LGA substrate. In someembodiments the interconnect of the additional die on the LGA substrateis by wire bonding to the LGA substrate; in some embodiments theinterconnect of the additional die on the LGA substrate is a is flipchip interconnect.

In another aspect the invention features a multi-package module havingstacked bottom and top packages, the bottom package being a BGA packageand the top package being an inverted LGA package, in which a thirdpackage is affixed upon the top LGA package. In some embodiments thethird package is a second inverted LGA package, and the z-interconnectbetween the third package is by wire bonding; in some embodiments thethird package is not inverted, and the z-interconnect with the invertedLGA package is by solder balls between ball pads on the lower surface(downward surface) of the third package and ball pads on the lowersurface (that is, the upward surface) of the inverted LGA package.

In another aspect the invention features a multi-package module havingstacked first (“bottom”) and second (“top”) packages, the bottom packagebeing a BGA package and the top package being a bump chip carrierpackage, in which the bump chip carrier package substrate and the BGApackage substrate are interconnected by wire bonding, and in which thebump chip carrier package is inverted so that the substrate surface towhich its die is attached is oriented downward.

In another general aspect the invention features a method for making amulti-package module, by providing a first (“bottom”) molded packageincluding a bottom package substrate and a die, dispensing adhesive ontoan upper surface of the bottom molded package, placing a second (“top”)package including a top package substrate and a die in an invertedorientation such that an upper (downward) surface of the top packagesubstrate contacts the adhesive on the upper surface of the bottompackage, curing the adhesive, and forming z-interconnects between thetop and bottom substrates.

In some embodiments the multi-package module includes a third oradditional packages, and the method includes affixing the third oradditional packages serially to form a stack.

In one aspect the invention features a method for making a multi-packagemodule including an inverted top package, which may be an LGA package ora bump chip carrier (“BCC”) package stacked over a bottom BGA package,in which the top and bottom packages are electrically interconnected bywire bonding. According to this aspect, a BGA package is provided,usually in an unsingulated strip of molded BGA packages; preferably theBGA packages in the strip are tested for performance and reliability andpackages identified as “good” are subjected to subsequent treatment;adhesive is dispensed over the upper surface of the molding on “good”BGA packages; a singulated (for example, saw-singulated) molded landgrid array package or bump chip carrier package is provided; preferablythe LGA package or BCC package is tested and identified as “good”; the“good” LGA or BCC package is inverted and placed onto the adhesive overthe molding on the “good” BGA package, and the adhesive is cured;optionally and preferably a plasma clean operation is performed followedby formation of wire bond z-interconnections between the stacked top andbottom packages; optionally and preferably an additional plasma cleanmay be performed, followed by the formation of the MPM molding. Furthersteps include attachment of second-level interconnect solder balls tothe underside of the module; testing and singulation of the completedmodule from the strip, for example by saw singulation or by punchsingulation; and packaging for further use.

In some embodiments the method includes steps for providing themulti-package module with a heat spreader. In this aspect of theinvention a similar process is performed, with additional stepsinterposed installation of supported heat spreader by a “drop-in” moldoperation, or for installation of a simple planar heat spreader by adrop-in mold operation; or by applying adhesive onto an upper surface ofthe top package molding or onto an upper surface of a spacer upon thetop package, and affixing the planar heat spreader onto the adhesive.

In another aspect the invention features a method for making amulti-package module including an inverted top package stacked over adie-down flip chip BGA bottom package, in which the top and bottompackages are electrically interconnected by wire bonding. According tothis aspect, a die-down flip chip BGA bottom package, optionally molded,is provided, usually in unsingulated strip of die-down flip chip ballgrid array bottom packages; preferably the BGA packages in the strip aretested for performance and reliability and packages identified as “good”are subjected to subsequent treatment; adhesive is dispensed onto theupper surface (back side) of the die on “good” BGA packages; singulatedtop (e.g., land grid array or bump chip carrier) packages, optionallymolded, are provided; preferably the LGA or BCC package is tested andidentified as “good”; the “good” LGA or BCC package is inverted andplaced onto the adhesive over the shield, and the adhesive is cured;optionally and preferably a plasma clean operation is performed followedby formation of wire bond z-interconnections between the stacked top andbottom packages; optionally and preferably an additional plasma cleanmay be performed, followed by the formation of the MPM molding. Furthersteps include attachment of second-level interconnect solder balls tothe underside of the module; testing and singulation of the completedmodule from the strip, for example by saw singulation or by punchsingulation; and packaging for further use.

In another aspect the invention features a method for making amulti-package module including an inverted top package stacked over adie-down flip chip BGA bottom package, in which the top and bottompackages are electrically interconnected by wire bonding, and in whichthe bottom package is provided with an electrical shield. According tothis aspect, a process is performed similar to that described above forthe unshielded bottom flip chip bottom package, with an additional stepinterposed for installation of the shield over the bottom package flipchip die. A die-down flip chip BGA bottom package, optionally molded, isprovided, usually in unsingulated strip of die-down flip chip ball gridarray bottom packages; preferably the BGA packages in the strip aretested for performance and reliability and packages identified as “good”are subjected to subsequent treatment; an electrical shield is affixedover the die on “good” bottom BGA packages; adhesive is dispensed ontothe upper surface of the shield on “good” BGA packages; singulated top(e.g., land grid array or bump chip carrier) packages, optionallymolded, are provided; preferably the LGA or BCC package is tested andidentified as “good”; the “good” LGA or BCC package is inverted andplaced onto the adhesive over the shield, and the adhesive is cured;optionally and preferably a plasma clean operation is performed followedby formation of wire bond z-interconnections between the stacked top andbottom packages; optionally and preferably an additional plasma cleanmay be performed, followed by the formation of the MPM molding. Furthersteps include attachment of second-level interconnect solder balls tothe underside of the module; testing and singulation of the completedmodule from the strip, for example by saw singulation or by punchsingulation; and packaging for further use.

In another aspect the invention features a method for making amulti-package module including an inverted top package stacked over adie-up flip chip BGA bottom package, in which the top and bottompackages are electrically interconnected by wire bonding. According tothis aspect, a die-up flip chip ball grid array package, usually notmolded, is provided, usually as an unsingulated strip of die-up flipchip ball grid array packages; preferably the BGA packages in the stripare tested for performance and reliability and packages identified as“good” are subjected to subsequent treatment; adhesive is dispensed overthe upper surface of the substrate on “good” BGA packages; a secondpackage is provided, which may in some embodiments be a stacked diepackage, optionally and usually molded; preferably the second package istested and identified as “good”; the “good” second package is invertedand placed onto the adhesive over the BGA substrate, and the adhesive iscured; optionally and preferably a plasma clean operation is performedfollowed by formation of wire bond z-interconnections between thestacked top and bottom packages; optionally and preferably an additionalplasma clean may be performed, followed by the formation of the MPMmolding. Further steps include attachment of second-level interconnectsolder balls to the underside of the module; testing and singulation ofthe completed module from the strip, for example by saw singulation orby punch singulation; and packaging for further use.

In another aspect the invention features a method for making amulti-package module including an inverted top package stacked over astacked die bottom package, in which the top and bottom packages areelectrically interconnected by wire bonding. According to this aspect, astacked die BGA package, usually molded, is provided, usually as anunsingulated strip of stacked die ball grid array packages is provided;preferably the BGA packages in the strip are tested for performance andreliability and packages identified as “good” are subjected tosubsequent treatment; adhesive is dispensed over the upper surface ofthe “good” stacked die BGA package, usually on the generally planarupper surface of the package molding; a singulated second package isprovided, usually molded, which may optionally be a stacked die package;preferably the second package is tested and identified as “good”; the“good” second package is inverted and placed onto the adhesive over theupper surface of the BGA, and the adhesive is cured; optionally andpreferably a plasma clean operation is performed followed by formationof wire bond z-interconnections between the stacked top and bottompackages; optionally and preferably an additional plasma clean may beperformed, followed by the formation of the MPM molding. Further stepsinclude attachment of second-level interconnect solder balls to theunderside of the module; testing and singulation of the completed modulefrom the strip, for example by saw singulation or by punch singulation;and packaging for further use.

In some embodiments of the method two or more first molded packages areprovided in an unsingulated strip, and assembly of the two or moremodules proceeds on the strip, and singulation of the two or moremodules is carried out after assembly has been completed.

In methods according to the invention for making multi-package modulesthe electrical connections between the stacked packages employsconventional wire bonding to form the z-interconnect between theinverted top package substrate and a bottom package substrate in thestack. Particular advantages include the use of establishedmanufacturing infrastructure, low production cost, design flexibility,and a thin package product. The wire bonding process may be carried outin either a “forward” or in a “reverse” manner. That is, thez-interconnect wire bonding can be carried out, in the various packageand module configurations, by drawing the wire to a conductive pad onthe first package substrate from a bump formed on a conductive pad onthe second package substrate; or, by drawing the wire to a conductivepad on the second package substrate from a bump formed on a conductivepad on the first package substrate.

The invention provides for assembly of more than one semiconductor in athin and minimal footprint package at the lowest cost and highest finaltest yield. Furthermore some stack configurations according to theinvention allow for high thermal performance, high electricalperformance or electrical isolation of an RF component from a digitalone. Other stack configurations provide a very thin structureappropriate for handheld or consumer products. All provide for a methodfor assembly that allows individual testing of the stacked packages tomaximize the final yield of the module.

Additional process steps will be employed to complete the multi-packagemodule according to the invention. For example, it may be preferred notto attach solder balls for connection of the lowermost package in thestack to the motherboard until the final step before singulation of theMPMs. And, for example, a plasma clean may be performed at any of avariety of points in the process, such as following adhesive cure andprior to encapsulation, and such as prior to and/or followingz-interconnect wire bonding.

Advantageously, the individual packages can be provided as strips ofseveral packages, connected in a row for ease of handling duringmanufacture, to be singulated following completion of process steps. Inmethods according to the invention, a strip of first packages of aselected type can be kept nonsingulated, and the package stacks can beformed on the strip by affixing singulated packages and forming the wirebonded z-interconnects serially until the process of forming the modulesis complete, and then singulating the modules.

MPM according to the invention can be used for building computers,telecommunications equipment, and consumer and industrial electronicsdevices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagrammatic sketch in a sectional view thru a conventionalball grid array semiconductor package.

FIG. 1B is a diagrammatic sketch in a sectional view thru a conventionalball grid array semiconductor package having a molding cap over theentire substrate surface, as for example a chip scale package.

FIG. 2 is a diagrammatic sketch in a sectional view thru a conventionalmulti-package module having solder ball z-interconnection betweenstacked ball grid array semiconductor packages.

FIG. 3 is a diagrammatic sketch in a sectional view thru a conventionalflip chip multi-package module having solder ball z-interconnectionbetween stacked flip chip semiconductor packages.

FIG. 4 is a diagrammatic sketch in a sectional view thru a conventionalmulti-package module having a folded flexible substrate and solder ballz-interconnection between stacked semiconductor packages.

FIG. 5A is a diagrammatic sketch in a sectional view thru an embodimentof a multi-package module having wire bond z-interconnection betweenstacked lower BGA and inverted upper LGA semiconductor packagesaccording to an aspect of the invention.

FIG. 5B is a sketch in a plan view showing bottom BGA z-interconnectbond pads in an arrangement suitable for use in an embodiment of theinvention as shown in FIG. 5A.

FIG. 5C is a sketch in a plan view showing top LGA z-interconnect bondpads in an arrangement suitable for use in an embodiment of theinvention as shown in FIG. 5A.

FIG. 5D is a diagrammatic sketch in a sectional view thru an embodimentof a multi-package module having wire bond z-interconnection betweenstacked lower BGA and inverted upper LGA semiconductor packages, havinga heatspreader over the inverted LGA, according to an aspect of theinvention.

FIG. 6A is a diagrammatic sketch in a sectional view thru an embodimentof a multi-package module having wire bond z-interconnection betweenstacked lower BGA and inverted upper LGA semiconductor packages, andhaving an electrical shield/heatspreader over the lower BGA and betweenthe lower BGA and the inverted upper LGA, according to a further aspectof the invention.

FIG. 6B is a diagrammatic sketch in a sectional view thru an embodimentof a multi-package module having wire bond z-interconnection betweenstacked lower BGA and inverted upper LGA semiconductor packages, andhaving an electrical shield/heatspreader over the lower BGA and betweenthe lower BGA and the inverted upper LGA as in FIG. 6A, and furtherhaving a heatspreader over the inverted LGA, according to a furtheraspect of the invention.

FIG. 7A is a diagrammatic sketch in a sectional view thru an embodimentof a multi-package module having wire bond z-interconnection betweenstacked bottom flip chip (die down) BGA and inverted top LGAsemiconductor packages according to a further aspect of the invention.

FIG. 7B is a diagrammatic sketch in a sectional view thru an embodimentof a multi-package module having wire bond z-interconnection betweenstacked bottom flip chip (die down) BGA and inverted top LGAsemiconductor packages according to a further aspect of the invention,the bottom package being provided with an electromagnetic shield/heatspreader.

FIG. 7C is a diagrammatic sketch in a sectional view thru an embodimentof a multi-package module having wire bond z-interconnection betweenstacked lower flip chip (die down) BGA and inverted upper LGAsemiconductor packages according to a further aspect of the invention,the bottom package being provided with an electromagnetic shield/heatspreader, and the module being further provided with a top heatspreader.

FIG. 8A is a diagrammatic sketch in a sectional view thru an embodimentof a multi-package module having wire bond z-interconnection betweenstacked bottom flip chip (die up) BGA and inverted top LGA semiconductorpackages according to a further aspect of the invention.

FIG. 8B is a diagrammatic sketch in a sectional view thru an embodimentof a multi-package module having wire bond z-interconnection betweenstacked bottom flip chip (die up) BGA and inverted top LGA semiconductorpackages according to a further aspect of the invention, the bottompackage being provided with an electromagnetic shield/heat spreader.

FIG. 8C is a diagrammatic sketch in a sectional view thru an embodimentof a multi-package module having wire bond z-interconnection betweenstacked lower flip chip (die up) BGA and inverted upper LGAsemiconductor packages according to a further aspect of the invention,the bottom package being provided with an electromagnetic shield/heatspreader, and the module being further provided with a top heatspreader.

FIG. 8D is a diagrammatic sketch in a sectional view thru an embodimentof a multi-package module having wire bond z-interconnection betweenstacked lower flip chip (die up) BGA and multiple inverted upper LGAsemiconductor packages according to a further aspect of the invention.

FIG. 9A is a diagrammatic sketch in a sectional view thru an embodimentof a multi-package module having wire bond z-interconnection betweenstacked lower BGA and inverted upper LGA semiconductor packagesaccording to a further aspect of the invention, in which each of theinverted upper LGA and lower BGA has stacked die wire-bonded to thesubstrate.

FIG. 9B is a diagrammatic sketch in a sectional view thru an embodimentof a multi-package module having wire bond z-interconnection betweenstacked lower BGA and inverted upper LGA semiconductor packagesaccording to a further aspect of the invention, in which each of theinverted upper LGA and lower BGA has stacked die wire-bonded to thesubstrate, and in which the module is provided with a top heat spreader.

FIG. 10A is a diagrammatic sketch in a sectional view thru an embodimentof a multi-package module having wire bond z-interconnection betweenstacked bottom BGA and inverted top semiconductor packages according toa further aspect of the invention, in which the top package is a BCCpackage.

FIG. 10B is a diagrammatic sketch in a sectional view thru an embodimentof a multi-package module having wire bond z-interconnection betweenstacked bottom BGA and inverted top semiconductor packages according toa further aspect of the invention, in which the top package is a BCCpackage having an additional die stacked on the BCC die.

FIG. 11A is a diagrammatic sketch in a sectional view thru an embodimentof a multi-package module having wire bond z-interconnection betweenstacked bottom BGA and inverted top LGA semiconductor packages accordingto a further aspect of the invention, in which the die in the bottom BGAis wire-bonded to the substrate, and in which a first die on thedownward facing surface of the inverted top LGA is wire-bonded to theLGA substrate and a second die on the opposite (upward facing) surfaceof the top LGA is flip-chip interconnected to the LGA substrate.

FIG. 11B is a diagrammatic sketch in a sectional view thru an embodimentof a multi-package module having wire bond z-interconnection betweenstacked bottom BGA and inverted top LGA semiconductor packages accordingto a further aspect of the invention, in which the die in the bottom BGAis wire-bonded to the substrate, and in which both a first die on thedownward facing surface of the inverted top LGA and a second die on theupward facing surface of the bottom package substrate are wire-bonded tothe top LGA substrate.

FIG. 11C is a diagrammatic sketch in a sectional view thru an embodimentof a multi-package module having wire bond z-interconnection betweenstacked bottom BGA and inverted top LGA semiconductor packages accordingto a further aspect of the invention, in which a third package isstacked over the inverted top LGA package, and is wire bonded thereto.

FIG. 11D is a diagrammatic sketch in a sectional view thru an embodimentof a multi-package module having wire bond z-interconnection betweenstacked bottom BGA and inverted top LGA semiconductor packages accordingto a further aspect of the invention, in which a third package isstacked over the inverted top LGA package, and is connected by solderballs thereto.

FIG. 12 is a flow diagram showing a process for assembly of amulti-package module according to the invention.

FIG. 13 is a flow diagram showing a process for assembly of amulti-package module according to the invention, in which the bottompackage is provided with a heat shield/heat spreader.

FIG. 14 is a flow diagram showing a process for assembly of amulti-package module according to the invention, in which the bottompackage is provided with a heat shield/heat spreader, and the module isfurther provided with a top heat spreader.

FIG. 15 is a flow diagram showing a process for assembly of amulti-package module according to the invention, in which the bottompackage is a flip chip package in a die-down configuration.

FIG. 16 is a flow diagram showing a process for assembly of amulti-package module according to the invention, in which the bottompackage is a flip chip package in a die-down configuration, and thepackage is provided with a top heat spreader.

FIG. 17 is a flow diagram showing a process for assembly of amulti-package module according to the invention, in which the bottompackage is a flip chip package in a die-up configuration.

FIG. 18 is a flow diagram showing a process for assembly of amulti-package module according to the invention, in which the top andbottom packages are stacked die packages.

DETAILED DESCRIPTION

The invention will now be described in further detail by reference tothe drawings, which illustrate alternative embodiments of the invention.The drawings are diagrammatic, showing features of the invention andtheir relation to other features and structures, and are not made toscale. For improved clarity of presentation, in the Figs. illustratingembodiments of the invention, elements corresponding to elements shownin other drawings are not all particularly relabeled, although they areall readily identifiable in all the Figs.

Turning now to FIG. 5A, there is shown in a diagrammatic sectional viewgenerally at 50 an embodiment of a multi-package module, includingstacked first (“bottom”) and second (“top”) packages, in which the toppackage is inverted, and the stacked packages are interconnected by wirebonding, according to an aspect of the invention. In the embodimentshown in FIG. 5A, the bottom package 400 is a conventional BGA packagesuch as that shown in FIG. 1A. Accordingly, in this embodiment thebottom package 400 includes a die 414 attached onto a bottom packagesubstrate 412 having at least one metal layer. Any of various substratetypes may be used, including for example: a laminate with 2-6 metallayers, or a build up substrate with 4-8 metal layers, or a flexiblepolyimide tape with 1-2 metal layers, or a ceramic multilayer substrate.The bottom package substrate 412 shown by way of example in FIG. 5A hastwo metal layers 421, 423, each patterned to provide appropriatecircuitry and connected by way of vias 422. The die is conventionallyattached to a surface of the substrate using an adhesive, typicallyreferred to as the die attach epoxy, shown at 413 in FIG. 5A and, in theconfiguration in FIG. 5A, the surface of the substrate onto which thedie is attached may be referred to as the “upper” surface, and the metallayer on that surface may be referred to as the “upper” metal layer,although the die attach surface need not have any particular orientationin use.

In the bottom BGA package of FIG. 5A the die is wire bonded onto wirebond sites on the upper metal layer of the substrate to establishelectrical connections. The die 414 and the wire bonds 416 areencapsulated with a molding compound 417 that provides protection fromambient and from mechanical stress to facilitate handling operations,and provides a bottom package upper surface 419 onto which a second(“top”) package can be stacked. The connections to the die are exposedat the periphery of the package with pads on the top metal layer of thesubstrate and available for connecting with wire bonds as described inmore detail below with reference to FIGS. 5B and 5C. These pads easilyfit within the space available between the lower BGA mold cap and theedge of the package, without increasing the overall footprint of theBGA. The physical location and order of these pads is arranged so as toapproximately lie under the equivalent pads on the LGA situated above.Solder balls 418 are reflowed onto bonding pads on the lower metal layerof the substrate to provide interconnection to underlying circuitry of,for example, a motherboard (not shown in the FIGS.) of a final product,such as a computer. Solder masks 415, 427 are patterned over the metallayers 421, 423 to expose the underlying metal at bonding sites forelectrical connection, for example the wire bond sites and bonding padsfor bonding the wire bonds 416 and solder balls 418.

In the embodiment shown in FIG. 5A, the top package 500 is a land gridarray (“LGA”) package which may be a saw singulated LGA package, asshown for example in FIG. 1B, and may be a chip scale package; but herethe top package has no solder balls mounted on bonding pads of the lowersurface of the substrate. Particularly, in this example, the top package500 includes a die 514 attached onto a top package substrate 512 havingat least one metal layer. Any of various substrate types may be used;the top package substrate 512 shown by way of example in FIG. 5A has twometal layers 521, 523, each patterned to provide appropriate circuitryand connected by way of vias 522. The die is conventionally attached toa surface of the substrate using an adhesive, typically referred to asthe die attach epoxy, shown at 513 in FIG. 5A. Referring again to FIGS.1A and 1B, the die is referred to as being attached to an upper surfaceof the package substrate, it being appreciated that the package need nothave any particular orientation in use. According to the invention, thetop package is inverted, that is to say, it is attached upside downwardand downside upward. Because the upper LGA is inverted in the module, sothat it is relatively speaking upside-down or downside-up, the surfaceof the upper LGA to which the first die is attached, which wouldcustomarily be termed the upper surface or upper side of the LGAsubstrate, is referred to in the text herein as the downward or downwardfacing surface of the inverted LGA; and the opposite surface, whichwould customarily be termed the lower surface or lower side, is referredto in the text herein as the upward or upward facing surface.

In the configuration in FIG. 5A, for example, the surface of the toppackage substrate onto which the die is attached faces toward the bottompackage, and, accordingly the “upper” surface of the top package, towhich the die is affixed, is here referred to as the “downward facing”surface of the top package substrate, it being appreciated again thatthe module need not have any particular orientation in use. That is tosay, once the top package has been inverted in the module according tothe invention, for purposes of description the surface of the toppackage substrate having the “upper” metal layer 521 is said to be“downward facing”, and the surface of the top package substrate havingthe “lower” metal layer 523 is said to be “upward facing”.

In the top LGA package in the embodiment of FIG. 5A the die is wirebonded onto wire bond sites on the upper metal layer of the top packagesubstrate to establish electrical connections. The die 514 and the wirebonds 516 are encapsulated with a molding compound 517 that providesprotection from ambient and from mechanical stress to facilitatehandling operations, and has a top package upper surface 519. The toppackage 500 is inverted (so that the surface 519 is “downward facing”,and is stacked over the bottom package 400 and affixed there using anadhesive 513. Solder masks 515, 527 are patterned over the metal layers521, 523 to expose the underlying metal at bonding sites for electricalconnection, for example the wire bond sites for bonding the wire bonds516.

The z-interconnect between the stacked top package 500 and bottompackage 400 is made by way of wire bonds 518 extending outwardly fromthe stacked top package 500 and connecting traces on the upward facingmetal layer (the “lower” metal layer 523) of the top package substratewith traces on the upper metal layer 421 of the bottom packagesubstrate. At one end each wire bond 518 is electrically connected toupward facing surfaces of pads on the lower metal layer 523 of the toppackage substrate 512, and at the other end each wire bond is connectedto upper surfaces of pads on the upper metal layer 421 of the bottompackage substrate 412. The wire bonds may be formed by any wire bondingtechnique, well known in the art, such as is described, for example, inU.S. Pat. No. 5,226,582, which is hereby incorporated by referenceherein. The package-to-package z-interconnect wire bonds are shown byway of example in FIG. 5A as having been made by forming a bead or bumpon the upper surface of a pad on the upper metal layer of the topsubstrate, and then drawing the wire downward toward and fusing it onto,a pad on the upper metal layer of the bottom substrate. As will beappreciated, the wire bonds can be made in the inverse direction, thatis, by forming a bead or bump on the upper surface of a pad on the uppermetal layer of the bottom substrate, and then drawing the wire upwardtoward and fusing it onto, a pad on the upper metal layer of the topsubstrate. As will be appreciated, selection of a wire bonding strategyfor the package-to-package z-interconnection will be determinedaccording to the geometric arrangements of the margins of the stackedsubstrates and of the bonding surfaces on them.

The top LGA package may be either array molded and saw singulated(giving vertical walls at the edges, as shown for example in FIG. 1B andas the upper LGA in FIG. 2, or cavity molded and punch singulated. Ineither type, the top package has bond pads connected to the die (throughvias to the die attach side of the substrate) and situated at theperiphery of the package on the substrate surface opposite the surfaceon which the die is attached, that is, on the “lower” (upward-facing)side of the top package substrate, as described in further detail belowwith reference to FIG. 5C.

The structure according to the invention allows for pre-testing of boththe BGA and LGA before assembly into the multi-package module, to permitrejection of nonconforming packages prior to assembly, and thereby toassure high final module test yields.

In the stacked package embodiment of FIG. 5A, the z-interconnect pads onthe respective package substrates are arranged on upward facing metallayers near the margins of the package substrates. The location andorder of the z-interconnect pads are generally arranged so that thez-interconnect pads on the top package substrate approximately overliethe corresponding z-interconnect pads on the bottom package when thepackages are stacked. Conveniently, the top package 500 has a smallersubstrate footprint than that of the bottom package 400, to allowclearance for the wire bonds without electrical shorting to the edges ofthe metal layers of the substrates. Once the z-interconnect wire bondshave been formed, a module encapsulation 507 is formed, to enclose andprotect the z-interconnect wire bonds and to provide mechanicalintegrity to the completed module. Accordingly, the module includesmolded packages within the module molding. As shown by way of example inFIG. 5A, the module may itself be saw-singulated; alternatively, themodule may be individually molded rather than saw-singulated.

The arrangements of the z-interconnect pads on the top and bottompackage substrates are shown by way of example in diagrammatic plan viewin FIGS. 5B and 5C, generally at 500 and 400, respectively. Referring toFIG. 5B, top package z-interconnect pads 524 are formed by patterningregions of the lower metal layer peripherally situated on the “lower”surface 525 of the top package substrate 512. As will be appreciated,when the top package is inverted, the “lower” substrate surface 525becomes the upward-facing surface of the top package substrate, and thetop package z-interconnect pads 524 are, accordingly, also upward-facingin the module. Also, as may be appreciated, the more centrally situatedball attach pads on the upward-facing side of the top package substrateare not necessary for z-interconnection and may be lacking in certainembodiments, depending upon the design of the top package. They areomitted, for illustrative purposes, from FIG. 5C.

Optionally, and in some applications preferably, the ball attach pads onthe upward-facing side of the inverted top package substrate may beemployed to facilitate testing of the LGA using a conventional testsocket. Such testing of the LGA can be carried out prior to attachingthe top LGA package into the bottom package, to ensure that only topLGAs testing as “good” are stacked over the bottom BGA packages (whichmay also be tested and identified as “good”). Or, testing of the LGA canbe carried out following inversion of the LGA and attachment as a toppackage, but prior to formation of the overall module molding, or priorto z-interconnect wire-bonding. Testing, facilitated according to theconstructs of the invention, at any of various stages in manufacture,can significantly reduce the likelihood of further processing ofcomponents that do not meet specifications.

Referring now to FIG. 5C, bottom package z-interconnect pads 424 areformed by patterning regions of the upper metal layer situated at themargin 401 on the upper surface 425 of the bottom package substrate 412.The margin 401 extends beyond the footprint 426 of the stacked andoverlying top package, defined by the edge 511 of the top packagesubstrate 512. The width of the margin 401 can be less about 1 mm, and,in order to provide adequate clearance for the wire bonding the width ofthe margin 401 may preferably be greater than about 0.2 mm. Nominally insome embodiments the margin 401 is about 0.5 mm. Where the module issaw-singulated, the margin constitutes approximately the clearancebetween the edge of the top package substrate and the side of the modulemolding.

The clearance between the z-interconnect wire bonds 518 and the uppersurface of the module molding may preferably be about 75 μm or greater,to avoid impact between the molding machinery and the wire loops duringmolding formation; and the molding thickness over the upward-facingsurface of the top package may preferably be greater than about 150 μm,to avoid formation of voids in the module molding. Where reverse wirebonding is employed, so that an end of the wire loop is stitched ontothe pads on the upward facing side of the top package, the wire loopheight in practice may be as little as about 75 μm and, accordingly, amolding thickness of as little as about 150 μm can be achieved in suchembodiments. A greater mold height will be required where forward wirebonding is employed, as the wire loop height over a ball (or bump) asmore usually about 125 μm or greater using currently available wirebonding techniques forming wire having about 1 mil thickness.

As will be apparent from FIGS. 5A, 5B and 5C, z-interconnection betweenthe top and bottom packages according to the invention is made by wirebond between (either bond-up or bond-down) the top package interconnectpads 524 in the margin 501 of the top package substrate and the bottompackage interconnect pads 424 in the margin 401 of the bottom packagesubstrate. The multipackage module structure is protected by formationof a module encapsulant 507, and solder balls 418 are reflowed ontoexposed solder ball pads on the lower metal layer of the bottom packagesubstrate, for connection to underlying circuitry, such as a motherboard(not shown in the FIGS.).

The multi-package module of the invention can be employed in any of adiverse variety of applications, such as, for example, computers,portable communications devices, consumer products.

For improved heat dissipation from the multi-package module, a heatspreader may be provided over the top package. The top heat spreader isformed of a thermally conductive material having at least the morecentral area of its upper surface exposed at the upper surface of theMPM to ambient for efficient heat exchange away from the MPM. The topheat spreader may be, for example, a sheet of metal (such as copper oraluminum) or of any of a variety of other thermally conductivematerials, such as aluminum nitride. The heat spreader has a size andshape to substantially cover the package. The heat spreader can be madethicker in a central area over the top package to increase metalcontent, and thinner at the periphery so that it does not interfere withthe z-interconnect wire bonds. If made thicker in a central area theheat spreader may be affixed to the upward facing surface of the toppackage. Or, a spacer may be placed over the upward facing surface ofthe package inboard of the wire bond sites, and the heat spreader may beaffixed to the upper surface of the spacer. Alternately the heatspreadercan be molded-in, resulting in a similar structure but without theadhesive; that is, the heat spreader may be dropped into the MPMencapsulant mold and affixed at the upper surface of the module duringthe molding material curing process. Or, the heatspreader may have agenerally planar portion over the top package, and a peripheralsupporting portion or supporting members resting on or near the uppersurface of the bottom package substrate.

For example, a top heat spreader having a thicker central region can beaffixed to the upward facing surface of the top package as showndiagrammatically in a sectional view in FIG. 5D. The construction of thestacked packages in MPM 52 is generally similar to that of MPM 50 inFIG. 5A, and like structures are identified in the FIGS. by likereference numerals. The top heat spreader 530 in the example of FIG. 5Dis a generally planar piece of a thermally conductive material having atleast the more central area of its planar upper surface exposed toambient for efficient heat exchange away from the MPM. The top heatspreader 530 has a thicker central portion, inboard of the wire bondsites on the top package, and the thicker portion is affixed to theupward facing side 519 of the top package using an adhesive 532. Thethickness of the heat spreader may in some embodiments be in the range0.2 to 0.6 mm, nominally 0.4 mm. The top heat spreader may be, forexample, constructed of metal (such as copper, or aluminum). Where thetop heat spreader is made of copper, the lower surface is preferablytreated to have a black oxide, for improved adhesion to the attachmentmaterial beneath; the exposed upper surface may be treated to form ablack oxide, or it may be provided with a matte nickel (plate) surface.The adhesive 532 may optionally be a thermally conductive adhesive, suchas a thermally conductive epoxy, to provide improved heat dissipation;and the adhesive may be electrically nonconductive, in embodimentshaving exposed electrical features on the upward facing (“lower”) side.Usually the top heat spreader is affixed to the top package before themolding material is injected for the MPM encapsulation 507. Theperiphery of the top heat spreader may be encapsulated with the MPMmolding material. In the embodiment of FIG. 5D a step like re-entrantfeature 534 is provided on the periphery of the heat spreader 530 toallow for better mechanical integrity of the structure with lessdelamination from the molding compound.

As a further alternative, an MPM as in FIG. 5A can be provided with atop heat formed of a thermally conductive material having a generallyplanar central portion situated over the top package, and peripheralsupporting members extending from near the edges or the corners of thegenerally planar central portion to the upper surface of the bottompackage substrate 412, outside the z-interconnect bond pads and near theedge of bottom package. The upper surface of the planar portion isexposed to ambient at the MPM upper surface for efficient heat exchangeaway from the MPM. The top heat spreader may be formed, for example, ofa sheet of metal (such as copper), for example by stamping. Thesupporting members can optionally be affixed to the upper surface of thebottom package substrate using an adhesive. The heat spreader supportingmembers are embedded in the MPM encapsulant 507 during the moldingmaterial curing process. As in the embodiment of FIG. 5D a step likere-entrant feature can be provided on the periphery of the planar upperportion of the heat spreader to allow for better mechanical integrity ofthe structure with less delamination from the molding compound. In thisembodiment the space between the lower surface of the planar centralportion of the heat spreader and the upward facing surface 519 of thetop package is filled by a thin layer of the MPM molding.

As a further alternative, an MPM as in FIG. 5A can be provided with asimple planar heat spreader, with no supporting members, that is notattached to the upper surface of the top package molding. In suchembodiments, as in the embodiment of FIG. 5D, the top heat spreader canbe a generally planar piece of a thermally conductive material such as,for example, a sheet of metal (such as copper or aluminum), and at leastthe more central area of the upper surface of the planar heat spreaderis exposed to ambient for efficient heat exchange away from the MPM.Here, the heat spreader does not have a thicker central portion inboardof the wire bond sites on the upper package; instead, the space betweenthe lower surface of the simple planar heat spreader and the uppersurface 519 of the top package may be filled by a thin layer of the MPMmolding, and such a simple planar heat spreader may be affixed to theMPM encapsulant 507 during the molding material curing process. Theperiphery of such an unattached simple planar top heat spreader can beencapsulated with the MPM molding material, as in the attached planarheat spreader of FIG. 5D, and may be provided with a step-likere-entrant feature on the periphery to allow for better mechanicalintegrity of the structure with less delamination from the moldingcompound.

An MPM structure having a heat spreader, as in FIG. 5D, or in thealternative embodiments described above, can provide significant thermalenhancement and may provide electrical shielding over the module, whichcan be critical to MPMs that combine RF and digital chips.

FIG. 6A is a diagrammatic sketch in a sectional view showing an invertedtop LGA package stacked over a BGA package in an MPM 60 according toanother aspect of the invention, in which a heat spreader/electricalshield is provided to the bottom package. The embodiment shown by way ofexample in FIG. 6A has a top land grid array (“LGA”) package 500inverted and stacked over a bottom ball grid array (“BGA”) package 400,in which the inverted top LGA package is constructed generally as is thetop LGA package in FIG. 5A. Referring to FIG. 6A, the top LGA package500 may be similar to a BGA package, as shown for example in FIG. 1A,but having no solder balls mounted on bonding pads of the lower surfaceof the substrate. Particularly, in this example, the top package 500includes a die 514 attached onto a top package substrate 512. Any ofvarious substrate types may be used; the top package substrate 512 shownby way of example in FIG. 6A has two metal layers 521, 523, eachpatterned to provide appropriate circuitry and connected by way of vias522. The die is conventionally attached to a surface of the substrateusing an adhesive, typically referred to as the die attach epoxy, shownat 513 in FIG. 6A and, in the configuration in FIG. 6A, the surface ofthe substrate onto which the die is attached may be referred to as the“upper” surface, and the metal layer on that surface may be referred toas the “upper” metal layer, although the die attach surface need nothave any particular orientation in use, and, for purposes of descriptionthe die attach side of the top package substrate is the downward facingside when the top package is inverted in the multi-package moduleaccording to the invention.

In the top LGA package in the embodiment of FIG. 6A the die is wirebonded onto wire bond sites on the upper metal layer of the substrate toestablish electrical connections. The die 514 and the wire bonds 516 areencapsulated with a molding compound 517 that provides protection fromambient and from mechanical stress to facilitate handling operations,and has a top package molding surface. In the inverted orientation thetop package molding surface is downward facing. Solder masks 515, 527are patterned over the metal layers 521, 523 to expose the underlyingmetal at bonding sites for electrical connection, for example the wirebond sites for bonding the wire bonds 516. In its inverted orientationin the multi-package module, the top package has an upward facingsurface 519.

The bottom BGA package 400 in the embodiment of FIG. 6A is aconventional BGA package such as that shown in FIG. 1A, except that thebottom BGA package of FIG. 6A is not encapsulated with a moldingcompound; rather, it is provided with a heat spreader that canadditionally act as an electrical shield, as described below.Accordingly, in this embodiment the bottom package 400 includes a die414 attached onto a bottom package substrate 412 having at least onemetal layer. Any of various substrate types may be used, including forexample: a laminate with 2-6 metal layers, or a build up substrate with4-8 metal layers, or a flexible polyimide tape with 1-2 metal layers, ora ceramic multilayer substrate. The bottom package substrate 412 shownby way of example in FIG. 6A has two metal layers 421, 423, eachpatterned to provide appropriate circuitry and connected by way of vias422. The die is conventionally attached to a surface of the substrateusing an adhesive, typically referred to as the die attach epoxy, shownat 413 in FIG. 6A and, in the configuration in FIG. 6A, the surface ofthe substrate onto which the die is attached may be referred to as the“upper” surface, and the metal layer on that surface may be referred toas the “upper” metal layer, although the die attach surface need nothave any particular orientation in use.

In the bottom BGA package of FIG. 6A the die is wire bonded onto wirebond sites on the upper metal layer of the substrate to establishelectrical connections. Solder balls 418 are reflowed onto bonding padson the lower metal layer of the substrate to provide interconnection tounderlying circuitry of, for example, a printed circuit board (not shownin the FIGS.) of a final product, such as a computer. Solder masks 415,427 are patterned over the metal layers 421, 423 to expose theunderlying metal at bonding sites for electrical connection, for examplethe wire bond sites and bonding pads for bonding the wire bonds 416 andsolder balls 418.

The bottom BGA package 400 of multipackage module 60 is provided with ametallic (for example, copper) heat spreader that acts additionally asan electrical shield to electrically contain any electromagneticradiation from the die in the lower BGA and thereby prevent interferencewith the die in the upper package. An “upper” planar part of the heatspreader 406 is supported above the substrate 412 and over the die 414by legs or vented sidewalls 407. Spots or lines 408 of an adhesive serveto affix the heat spreader support 407 to the upper surface of thebottom substrate. The adhesive can be a conductive adhesive, and can beelectrically connected to the top metal layer 421 of the substrate 412,particularly to a ground plane of the circuit and thereby establishingthe heat spreader as an electrical shield. To provide good shielding,the electric shield is constructed of a highly electrically conductivematerial, usually a metal such as aluminum or copper. Where it iscopper, the copper surface is preferably treated to provide a blackoxide surface, or is provided with a nickel plating, to improveadhesion. Or, the adhesive can be non-conductive and in such aconfiguration the heat spreader acts only as a heat spreading device.The supporting parts and the top part of the heat spreader 406 enclosethe die 414 and the wire bonds 416, and can serve to protect thosestructures from ambient and from mechanical stress to facilitatehandling operations and, particularly, during subsequent testing beforethe MPM assembly. Accordingly, no separate bottom package molding isnecessary in such embodiments (the MPM molding, fills in later), makingfor decreased manufacturing cost.

The top package 500 of multipackage module 60 is stacked over the bottompackage 400 upon the planar surface of the heat spreader/shield 406 andaffixed there using an adhesive 503. The adhesive 503 can be thermallyconductive, to improve thermal dissipation.

The z-interconnection between the top package 500 and the bottom package400 according to the invention is made by wire bonds 518 between toppackage interconnect pads in the margin of the top package substrate 512and bottom package interconnect pads in the margin of the bottom packagesubstrate 400. The wire bonds may be formed in either up-bond ordown-bond (forward or reverse bond) fashion. The multipackage modulestructure is protected by formation of a module encapsulant 607.Openings (vents) may be provided in the supporting parts 407 of the heatspreader to allow the MPM molding material to fill in the enclosed spaceduring encapsulation.

Solder balls 418 are reflowed onto exposed solder ball pads on the lowermetal layer of the bottom package substrate 412, for connection tounderlying circuitry, such as a printed circuit board (not shown in theFIGS.) such as a motherboard.

Multi-package modules according to this aspect of the invention, inwhich an electric shield is provided over the bottom package, can beparticularly useful in radio-frequency devices, as for example incommunications equipment. In applications having digital and RFsemiconductor chips, the electronic shield can provide noise reductionby suppressing RF interference either to or from the shielded die. Thiscan be particularly useful for example where the bottom packagesemiconductor die is a radio-frequency device, as for example incommunications equipment, to prevent electromagnetic interferencebetween the RF die and the upper package.

As will be appreciated from the foregoing, the structure according tothe invention allows for pre-testing of both the BGA and LGA beforeassembly into the multi-package module, to permit rejection ofnonconforming packages prior to assembly, and thereby to assure highfinal module test yields.

For improved heat dissipation from the multi-package module, a top heatspreader may be provided over the top package in addition to the heatspreader/electrical shield over the bottom package as in FIG. 6A. Thetop heat spreader is formed of a thermally conductive material having atleast the more central area of its upper surface exposed at the uppersurface of the MPM to ambient for efficient heat exchange away from theMPM. The top heat spreader may be, for example, a sheet of metal (suchas copper or aluminum) or of any of a variety of other thermallyconductive materials, such as aluminum nitride. The heat spreader has asize and shape to substantially cover the package. The heat spreader canbe made thicker in a central area over the top package to increase metalcontent, and thinner at the periphery so that it does not interfere withthe z-interconnect wire bonds. If made thicker in a central area theheat spreader may be affixed to the upward facing surface of the toppackage. Or, a spacer may be placed over the upward facing surface ofthe package inboard of the wire bond sites, and the heat spreader may beaffixed to the upper surface of the spacer. Alternately the heatspreadercan be molded-in, resulting in a similar structure but without theadhesive; that is, the heat spreader may be dropped into the MPMencapsulant mold and affixed at the upper surface of the module duringthe molding material curing process. Or, the heatspreader may have agenerally planar portion over the top package, and a peripheralsupporting portion or supporting members resting on or near the uppersurface of the bottom package substrate.

For example, a top heat spreader having a thicker central region can beaffixed to the upward facing surface of the top package as showndiagrammatically in a sectional view in FIG. 6B. The construction of thestacked packages in MPM 62 is generally similar to that of MPM 60 inFIG. 6A, and like structures are identified in the FIGS. by likereference numerals. The top heat spreader 530 in the example of FIG. 6Bis a generally planar piece of a thermally conductive material having atleast the more central area of its planar upper surface exposed toambient for efficient heat exchange away from the MPM. The top heatspreader 530 has a thicker central portion, inboard of the wire bondsites on the top package, and the thicker portion is affixed to theupward facing side 519 of the top package using an adhesive 532. Thethickness of the heat spreader may in some embodiments be in the range0.2 to 0.6 mm, nominally 0.4 mm. The top heat spreader may be, forexample, constructed of metal (such as copper, or aluminum). Where thetop heat spreader is made of copper, the lower surface is preferablytreated to have a black oxide, for improved adhesion to the attachmentmaterial beneath; the exposed upper surface may be treated to form ablack oxide, or it may be provided with a matte nickel (plate) surface.The adhesive 532 may optionally be a thermally conductive adhesive, suchas a thermally conductive epoxy, to provide improved heat dissipation;and the adhesive may be electrically nonconductive, in embodimentshaving exposed electrical features on the upward facing (“lower”) side.Usually the top heat spreader is affixed to the top package before themolding material is injected for the MPM encapsulation 607. Theperiphery of the top heat spreader may be encapsulated with the MPMmolding material. In the embodiment of FIG. 6B a step like re-entrantfeature 534 is provided on the periphery of the heat spreader 530 toallow for better mechanical integrity of the structure with lessdelamination from the molding compound.

As a further alternative, an MPM as in FIG. 6A can be provided with atop heat formed of a thermally conductive material having a generallyplanar central portion situated over the top package, and peripheralsupporting members extending from near the edges or the corners of thegenerally planar central portion to the upper surface of the bottompackage substrate 412, outside the z-interconnect bond pads and near theedge of bottom package. The upper surface of the planar portion isexposed to ambient at the MPM upper surface for efficient heat exchangeaway from the MPM. The top heat spreader may be formed, for example, ofa sheet of metal (such as copper), for example by stamping. Thesupporting members can optionally be affixed to the upper surface of thebottom package substrate using an adhesive. The heat spreader supportingmembers are embedded in the MPM encapsulant 607 during the moldingmaterial curing process. As in the embodiment of FIG. 6B a step likere-entrant feature can be provided on the periphery of the planar upperportion of the heat spreader to allow for better mechanical integrity ofthe structure with less delamination from the molding compound. In thisembodiment the space between the lower surface of the planar centralportion of the heat spreader and the upward facing surface 519 of thetop package is filled by a thin layer of the MPM molding.

As a further alternative, an MPM as in FIG. 6A can be provided with asimple planar heat spreader, with no supporting members, that is notattached to the upper surface of the top package molding. In suchembodiments, as in the embodiment of FIG. 6B, the top heat spreader canbe a generally planar piece of a thermally conductive material such as,for example, a sheet of metal (such as copper or aluminum), and at leastthe more central area of the upper surface of the planar heat spreaderis exposed to ambient for efficient heat exchange away from the MPM.Here, the heat spreader does not have a thicker central portion inboardof the wire bond sites on the upper package; instead, the space betweenthe lower surface of the simple planar heat spreader and the uppersurface 519 of the top package may be filled by a thin layer of the MPMmolding, and such a simple planar heat spreader may be affixed to theMPM encapsulant 607 during the molding material curing process. Theperiphery of such an unattached simple planar top heat spreader can beencapsulated with the MPM molding material, as in the attached planarheat spreader of FIG. 5D, and may be provided with a step-likere-entrant feature on the periphery to allow for better mechanicalintegrity of the structure with less delamination from the moldingcompound.

An MPM structure having a heat spreader, as in FIG. 6B, or in thealternative embodiments described above, can provide significant thermalenhancement and may provide electrical shielding over the module, whichcan be critical to MPMs that combine RF and digital chips.

An advantage of a structure as in FIGS. 5D, 6A, 6B is significantthermal performance and, optionally, electrical shielding at the bottompackage, which can be particularly important critical, for example, inMPM that combine RF and digital chips. It is not necessary to have botha bottom package heat spreader and a top heat spreader for allapplications. Alternately one or the other may be adequate depending onthe end product needs.

As may be appreciated, either or both of the packages may have flipchip, rather than wire bonding, interconnection of the die to therespective package substrates, but according to the invention the toppackage is inverted, and z-interconnection between the top and bottomsubstrates is by wire bonding.

In some modules having flip chip interconnection of the bottom packagedie to the bottom package substrate, for example, the die in the bottomBGA may be interconnected with the bottom BGA substrate by flip-chipinterconnect in a “die down” configuration. No separate molding isrequired for the lower BGA package in this configuration; a matrix moldsaw-singulated molding encapsulates the upper LGA package, and an MPMmolding encapsulates the stacked packages in the completed multi-packagemodule.

FIG. 7A is a diagrammatic sketch in a sectional view showing amulti-package module 70 according to another aspect of the invention, inwhich an inverted top package is stacked over a flip chip BGA with diedown. In the lower BGA the die is flip chip connected to the substrateand the space between the die and the substrate is underfilled. This BGAcan be tested before assembly into the MPM. The back of the die isavailable to attach the inverted top LGA with adhesive. Thez-interconnect of the top LGA to the module substrate is via wirebonding and the MPM is molded. A primary advantage of this configurationis that the flip chip connection on the BGA provides for high electricalperformance.

Referring to FIG. 7A, the bottom BGA flip chip package includes asubstrate 412 having a patterned metal layer 321 onto which the die 314is connected by flip chip bumps 316, such as solder bumps, gold studbumps or anisotropically conducting film or paste. Any of varioussubstrate types may be used; the bottom package substrate 312 shown byway of example in FIG. 7A has two metal layers 321, 323, each patternedto provide appropriate circuitry and connected by way of vias 322. Theflip chip bumps are affixed to a patterned array of bump pads on theactive surface of the die and, as the active surface of the die facesdownward in relation to an upward-facing patterned metal layer of thesubstrate, such an arrangement may be referred to as a “die down” flipchip package. A polymer underfill 313 between die and substrate providesprotection from ambient and adds mechanical integrity to the structure.

The top LGA package 500 of multipackage module 70 is constructedgenerally similarly to the top LGA package 500 of the multipackagemodule 50 of FIG. 5A. Particularly, the top package 500 includes a die514 attached onto a top package substrate 512. Any of various substratetypes may be used; the top package substrate 512 shown by way of examplein FIG. 7A has two metal layers 521, 523, each patterned to provideappropriate circuitry and connected by way of vias 522. The die isconventionally attached to a surface of the substrate using an adhesive,typically referred to as the die attach epoxy, shown at 513 in FIG. 7Aand, in the configuration in FIG. 7A, the surface of the substrate ontowhich the die is attached may be referred to as the “upper” surface, andthe metal layer on that surface may be referred to as the “upper” metallayer, although the die attach surface need not have any particularorientation in use, and, for purposes of description the die attach sideof the upper package substrate is the downward facing side when the toppackage is inverted in the multi-package module according to theinvention.

In the top LGA package 500 in the embodiment of FIG. 7A the die is wirebonded onto wire bond sites on the upper metal layer of the substrate toestablish electrical connections. The die 514 and the wire bonds 516 areencapsulated with a molding compound 517 that provides protection fromambient and from mechanical stress to facilitate handling operations,and has a top package molding surface. In the inverted orientation thetop package molding surface is downward facing. Solder masks 515, 527are patterned over the metal layers 521, 523 to expose the underlyingmetal at bonding sites for electrical connection, for example the wirebond sites for bonding the wire bonds 516. In its inverted orientationin the multi-package module, the top package has an upward facing(“lower”) surface 519.

The top package 500 is stacked over the bottom package 300 and affixedthere using an adhesive, indicated at 503.

The z-interconnect between the stacked top package 500 and bottompackage 300 is made by way of wire bonds 518 connecting theupward-facing metal layers of the respective package substrates. Themultipackage module structure is protected by formation of a moduleencapsulant 707, and solder balls 318 are reflowed onto exposed solderball pads on the lower metal layer of the bottom package substrate, forconnection to underlying circuitry, such as a motherboard (not shown inthe FIGS.) of a final product, such as a computer. Solder masks 315, 327are patterned over the metal layers 321, 323 to expose the underlyingmetal at bonding sites for electrical connection, for example the wirebond sites and bonding pads for bonding the wire bonds 518 and solderballs 318.

Structures having a LGA stacked over a flip chip BGA with die down asdescribed for example with reference to FIG. 7A can be assembled with aheat spreader/electrical shield much as shown in FIG. 6A or FIG. 6B.Accordingly, FIG. 7B is a diagrammatic sketch in a sectional viewshowing a multi-package module according to another aspect of theinvention, in which an inverted LGA is stacked over a flip chip BGA withdie down, as in the embodiment of FIG. 7A, and in which the lower BGA isprovided with a heat spreader/shield.

Particularly, referring to FIG. 7B, the bottom BGA package 300 ofmultipackage module 72 is provided with a metallic (for example, copper)heat spreader that acts additionally as an electrical shield toelectrically contain any electromagnetic radiation from the die in thelower BGA and thereby prevent interference with the die in the upperpackage. An upper planar part of the heat spreader 406 is supportedabove the substrate 312 and over the die 314 by legs or sidewalls 407.Spots or lines 408 of an adhesive serve to affix the heat spreadersupport 406 to the upper surface of the bottom substrate. The adhesivecan be a conductive adhesive, and can be electrically connected to thetop metal layer 321 of the substrate 312, particularly to a ground planeof the circuit and thereby establishing the heat spreader as anelectrical shield. Or, the adhesive can be non-conductive and in such aconfiguration the heat spreader acts only as a heat spreading device.The supporting parts and the top part of the heat spreader 406 enclosethe die 314, and can serve for protection from ambient and frommechanical stress to facilitate handling operations and, particularly,during subsequent testing before the MPM assembly.

The top package 500 of multipackage module 72 is stacked over the bottompackage 300 upon the planar surface of the heat spreader/shield 406 andaffixed there using an adhesive 503. The adhesive 503 can be thermallyconductive, to improve thermal dissipation; and the adhesive 503 can beelectrically conductive, to establish electrical connection of the heatspreader 406 to a lower metal layer of the LGA package substrate, or itcan be electrically insulating, thereby preventing electricalconnection.

The z-interconnection between the top package 500 and the bottom package300 according to the invention is made by wire bonds 518 between toppackage interconnect pads in the margin of the top package substrate 512and bottom package interconnect pads in the margin of the bottom packagesubstrate 300. The wire bonds may be formed in either up-bond ordown-bond (forward or reverse bonding) fashion. The multipackage modulestructure is protected by formation of a module encapsulant 707.Openings may be provided in the supporting parts 407 of the heatspreader to allow the MPM molding material to fill in the enclosed spaceduring encapsulation.

Solder balls 318 are reflowed onto exposed solder ball pads on the lowermetal layer of the bottom package substrate 300, for connection tounderlying circuitry, such as a printed circuit board (not shown in theFIGS.).

As will be appreciated from the foregoing, the structure according tothe invention allows for pre-testing of both the BGA and LGA beforeassembly into the multi-package module, to permit rejection ofnonconforming packages prior to assembly, and thereby to assure highfinal module test yields.

The processor chip in a flip chip bottom package according to thisaspect of the invention can be, for example, an ASIC, or a GPU, or aCPU, often an ASIC; and the top package can be, for example, a processorchip or, for example, a memory package or an ASIC package. Where the toppackage is a memory package it can be a stacked die memory package. Ashielded flip chip die-down bottom package can be particularly suitablefor higher speed applications, particularly for RF frequency processing,as in mobile communications applications.

Optionally, for improved heat dissipation from the multi-package module,a MPM having a flip chip bottom package in a die-down configuration (asshown for example in FIG. 7A or FIG. 7B) may be further provided with atop heat spreader over the top package in addition to the heatspreader/electrical shield over the bottom package as in FIG. 7B. Theoptional top heat spreader is formed of a thermally conductive materialhaving at least the more central area of its upper surface exposed atthe upper surface of the MPM to ambient for efficient heat exchange awayfrom the MPM. The top heat spreader may be, for example, a sheet ofmetal (such as copper or aluminum) or of any of a variety of otherthermally conductive materials, such as aluminum nitride. The heatspreader has a size and shape to substantially cover the package. Theheat spreader can be made thicker in a central area over the top packageto increase metal content, and thinner at the periphery so that it doesnot interfere with the z-interconnect wire bonds. If made thicker in acentral area the heat spreader may be affixed to the upward facingsurface of the top package. Or, a spacer may be placed over the upwardfacing surface of the package inboard of the wire bond sites, and theheat spreader may be affixed to the upper surface of the spacer.Alternately the heatspreader can be molded-in, resulting in a similarstructure but without the adhesive; that is, the heat spreader may bedropped into the MPM encapsulant mold and affixed at the upper surfaceof the module during the molding material curing process. Or, theheatspreader may have a generally planar portion over the top package,and a peripheral supporting portion or supporting members resting on ornear the upper surface of the bottom package substrate.

For example, a top heat spreader having a thicker central region can beaffixed to the upward facing surface of the top package as showndiagrammatically in a sectional view in FIG. 7C. The construction of thestacked packages in MPM 74 is generally similar to that of MPM 72 inFIG. 7B, and like structures are identified in the FIGS. by likereference numerals. The top heat spreader 530 in the example of FIG. 7Cis a generally planar piece of a thermally conductive material having atleast the more central area of its planar upper surface exposed toambient for efficient heat exchange away from the MPM. The top heatspreader 530 has a thicker central portion, inboard of the wire bondsites on the top package, and the thicker portion is affixed to theupward facing side 519 of the top package using an adhesive 532. Thethickness of the heat spreader may in some embodiments be in the range0.2 to 0.6 mm, nominally 0.4 mm. The top heat spreader may be, forexample, constructed of metal (such as copper, or aluminum). Where thetop heat spreader is made of copper, the lower surface is preferablytreated to have a black oxide, for improved adhesion to the attachmentmaterial beneath; the exposed upper surface may be treated to form ablack oxide, or it may be provided with a matte nickel (plate) surface.The adhesive 532 may optionally be a thermally conductive adhesive, suchas a thermally conductive epoxy, to provide improved heat dissipation;and the adhesive may be electrically nonconductive, in embodimentshaving exposed electrical features on the upward facing (“lower”) side.Usually the top heat spreader is affixed to the top package before themolding material is injected for the MPM encapsulation 707. Theperiphery of the top heat spreader may be encapsulated with the MPMmolding material. In the embodiment of FIG. 7C a step like re-entrantfeature 534 is provided on the periphery of the heat spreader 530 toallow for better mechanical integrity of the structure with lessdelamination from the molding compound.

As a further alternative, an MPM as in FIG. 7A or FIG. 7B can beprovided with a top heat spreader formed of a thermally conductivematerial having a generally planar central portion situated over the toppackage, and peripheral supporting members extending from near the edgesor the corners of the generally planar central portion to the uppersurface of the bottom package substrate 312, outside the z-interconnectbond pads and near the edge of bottom package. The upper surface of theplanar portion is exposed to ambient at the MPM upper surface forefficient heat exchange away from the MPM. The top heat spreader may beformed, for example, of a sheet of metal (such as copper), for exampleby stamping. The supporting members can optionally be affixed to theupper surface of the bottom package substrate using an adhesive. Theheat spreader supporting members are embedded in the MPM encapsulant 707during the molding material curing process. As in the embodiment of FIG.6B a step like re-entrant feature can be provided on the periphery ofthe planar upper portion of the heat spreader to allow for bettermechanical integrity of the structure with less delamination from themolding compound. In this embodiment the space between the lower surfaceof the planar central portion of the heat spreader and the upward facingsurface 519 of the top package is filled by a thin layer of the MPMmolding.

As a further alternative, an MPM as in FIG. 7A or FIG. 7B can beprovided with a simple planar heat spreader, with no supporting members,that is not attached to the upper surface of the top package molding. Insuch embodiments, as in the embodiment of FIG. 6B, the top heat spreadercan be a generally planar piece of a thermally conductive material suchas, for example, a sheet of metal (such as copper or aluminum), and atleast the more central area of the upper surface of the planar heatspreader is exposed to ambient for efficient heat exchange away from theMPM. Here, the heat spreader does not have a thicker central portioninboard of the wire bond sites on the upper package; instead, the spacebetween the lower surface of the simple planar heat spreader and theupward facing surface 519 of the top package may be filled by a thinlayer of the MPM molding, and such a simple planar heat spreader may beaffixed to the MPM encapsulant 707 during the molding material curingprocess. The periphery of such an unattached simple planar top heatspreader can be encapsulated with the MPM molding material, as in theattached planar heat spreader of FIG. 7C, and may be provided with astep-like re-entrant feature on the periphery to allow for bettermechanical integrity of the structure with less delamination from themolding compound.

An MPM structure having a heat spreader, as in FIG. 7C, or in thealternative embodiments described above, can provide significant thermalenhancement and may provide electrical shielding over the module, whichcan be critical to MPMs that combine RF and digital chips.

An advantage of a structure as in FIGS. 7B, 7C is significant thermalperformance and, optionally, electrical shielding at the bottom package,which can be particularly important critical, for example, in MPM thatcombine RF and digital chips. It is not necessary to have both a bottompackage heat spreader and a top heat spreader for all applications.Alternately one or the other may be adequate depending on the endproduct needs.

In some modules having flip chip interconnection of the bottom packagedie to the bottom package substrate, for example, the die in the bottomBGA may be interconnected with the bottom BGA substrate by flip-chipinterconnect in a “die up” configuration, in which the bottom packagedie is carried on the lower surface of the bottom package substrate.Usually the bottom package die attach region in such a configuration issituated about the center of the substrate area, and the second-levelinterconnect balls are arranged peripherally near two or (more usually)all four of the substrate edges. The die-up flip chip and its flip chipinterconnect structures are located within the standoff height of thesecond-level interconnect structures, and, accordingly, the bottompackage die in such configurations contributes nothing to the overallthickness of the MPM. Such a configuration can provide higher electricalperformance in the bottom package (and, therefore, in the module) notonly because flip chip interconnect is employed but also because theconnection of the die to the solder balls is more direct and requiresshorter metal traces, and avoids vias. Moreover, the die-upconfiguration can avoid a netlist inversion effect, which typically is aconsequence of die-down configuration, which may be desirable in someapplications. As is well known, a die arranged to face upward (die-up)has a netlist that is the mirror image of the same die when facingdownward (die-down). No separate molding is required for the lower BGApackage in this configuration; a matrix mold saw-singulated moldingencapsulates the inverted upper LGA package, and an MPM moldingencapsulates the stacked packages in the completed multi-package module.

Particularly, by way of example, FIG. 8A is a diagrammatic sketch in asectional view showing a multi-package module 80 according to anotheraspect of the invention, in which an inverted land grid array package500 is stacked over a flip chip BGA in a die-up configuration 302, andthe stacked packages are interconnected by wire bonding. In the bottomBGA package 302 the die 344 is attached on the lower side of the BGAsubstrate 342.

As the FIG. illustrates, this structure provides for a thinner MPMbecause the bottom package die is on the underside of the bottom packagein the area between the peripherally situated solder balls. Such aconfiguration can have a higher electrical performance not only becauseit employs a flip chip connection but also because it provides moredirect electrical connection of the die to the solder balls, withshorter metal traces and without requiring vias (as are required in aconfiguration as in FIG. 7A or 7B or 7C) for connection between the dieand the solder balls. Furthermore the die-up configuration enables thispackage to be netlist compatible to wire bonding, as may be desired insome applications. Netlist is the sum of all pairs of connectionsbetween the die and the solder balls. When the die faces up “die-down”it has a connection pattern that is the mirror image of the pattern inthe same die when the die is facing down “die-up”.

In a configuration as in FIG. 8A the top LGA package is inverted andattached with adhesive onto the upper side of the BGA, and then is wirebonded and the module is molded. The bottom flip chip BGA package 302includes a substrate 342 having a patterned metal layer 353 onto partsof which the die 344 is connected by flip chip bumps 346, such as solderbumps, gold stud bumps or anisotropically conducting film or paste. Anyof various substrate types may be used; the bottom package substrate 342shown by way of example in FIG. 8A has two metal layers 351, 353, eachpatterned to provide appropriate circuitry. Bottom package substrate 342additionally has a metal layer 355 sandwiched between dielectric layers354, 356. Metal layer 355 has voids at selected locations, to permitconnection of the metal layers 351, 353 by vias therethrough and,accordingly, selected parts of the patterned metal layers 351, 353 areconnected by way of vias through the substrate layers 354, 356 andthrough the voids in the sandwiched metal layer 355. Selected parts ofthe patterned metal layer 353 are connected by way of vias throughsubstrate layer 356 to sandwiched metal layer 355.

Flip chip bumps 346 are attached to a patterned array of bump pads onthe active surface of the die 344 and, as the active surface of the diefaces upward in relation to an downward-facing patterned metal layer ofthe substrate, such an arrangement may be referred to as a “die up” flipchip package. A polymer underfill 343 between the die and the die attachregion of the substrate provides protection from ambient and addsmechanical integrity to the structure.

As noted above, the metal layers 351, 353 are patterned to provideappropriate circuitry, and the sandwiched metal layer 355 has voids atselected locations to allow interconnections (without contact with thesandwiched metal layer 355) between selected traces on the upper andlower metal layers 351, 353. Particularly, for example, the lower metallayer is patterned in the die attach area to provide attachment sitesfor the flip chip interconnect bumps 353; and, for example, the lowermetal layer is patterned nearer the margin of the bottom packagesubstrate 342 to provide attachment sites for the second-levelinterconnect solder balls 348, by which the completed MPM is attached bysolder reflow to underlying circuitry (not shown). And particularly, forexample, the upper metal layer is patterned near the margin of thebottom package substrate 342 to provide attachment sites for wire bondsconnecting the top package to the bottom package. Ground lines in thecircuitry of metal layer 353 are connected through vias to thesandwiched metal layer 355; selected ones of the solder balls 348 areground balls, which will be attached to ground lines in the underlyingcircuitry when the MPM is installed. Thus, the sandwiched metal layer355 serves as a ground plane for the MPM. Selected others of the solderballs 348 are input/output balls or power balls, and these are,accordingly, attached to solder ball sites on input/output or powerlines, respectively, in the circuitry of metal layer 353.

Referring still to FIG. 8A, the top package 500 is constructed generallysimilarly to the top LGA package 500 of the multipackage module 50 ofFIG. 5A. Particularly, the top package 500 includes a die 514 attachedonto a top package substrate 512. Any of various substrate types may beused; the top package substrate 512 shown by way of example in FIG. 8A,as in the top package substrate of FIG. 5A, has two metal layers, eachpatterned to provide appropriate circuitry and connected by way of vias.The die is conventionally attached to a surface of the substrate usingan adhesive, typically referred to as the die attach epoxy, shown at 513in FIG. 8A and, in the configuration in FIG. 8A, the surface of thesubstrate onto which the die is attached may be referred to as the“upper” surface, and the metal layer on that surface may be referred toas the “upper” metal layer, although the die attach surface need nothave any particular orientation in use, and, for purposes of descriptionthe die attach side of the upper package substrate is the downwardfacing side when the top package is inverted in the multi-package moduleaccording to the invention.

In the top LGA package 500 in the embodiment of FIG. 8A the die is wirebonded onto wire bond sites on the upper metal layer of the substrate toestablish electrical connections. The die 514 and the wire bonds 516 areencapsulated with a molding compound 517 that provides protection fromambient and from mechanical stress to facilitate handling operations,and has a top package molding surface. In the inverted orientation thetop package molding surface is downward facing. Solder masks arepatterned over the respective metal layers to expose the underlyingmetal at bonding sites for electrical connection, for example the wirebond sites for bonding the wire bonds 516. In its inverted orientationin the multi-package module, the top package has an upward facing(“lower”) surface 519.

The top package 500 is inverted and stacked over the bottom package 300,that is to say, over the upper surface of the bottom package substrate342, and affixed there using an adhesive, indicated at 503.

The z-interconnect between the stacked top package 500 and bottompackage 300 is made by way of wire bonds 518 connecting theupward-facing metal layers of the respective package substrates. Themultipackage module structure is protected by formation of a moduleencapsulant 807, and solder balls 318 are reflowed onto exposed solderball pads on the lower metal layer of the bottom package substrate, forconnection to underlying circuitry, such as a motherboard (not shown inthe FIGS.) of a final product, such as a computer.

Structures having a LGA stacked over a flip chip BGA with die up asdescribed for example with reference to FIG. 8A can be assembled with aheat spreader/electrical shield around the bottom package die much asshown in FIG. 6A or FIG. 6B. Accordingly, FIG. 8B is a diagrammaticsketch in a sectional view showing a multi-package module according toanother aspect of the invention, in which an inverted LGA is stackedover a flip chip BGA with die up, as in the embodiment of FIG. 8A, andin which the lower BGA is provided with a heat spreader/shield.

Particularly, referring to FIG. 8B, the bottom BGA package 300 ofmultipackage module 82 is provided with a metallic (for example, copper)heat spreader that surrounds the die and acts additionally as anelectrical shield to electrically contain any electromagnetic radiationfrom the die in the lower BGA and thereby prevent interference with thedie in the upper package. A lower planar part 304 of the heat spreaderis supported on the substrate 342 by legs or sidewalls 305. Spots orlines 306 of an adhesive serve to affix the heat spreader supports 305to the lower surface of the bottom package substrate. The adhesive canbe a conductive adhesive, and can be electrically connected to the lowermetal layer 353 of the substrate 342, particularly to a ground plane ofthe circuit and thereby establishing the heat spreader as an electricalshield. Or, the adhesive can be non-conductive and in such aconfiguration the heat spreader acts only as a heat spreading device.Alternatively, the shield enclosing the upward-facing bottom package diecan be soldered or affixed using adhesive to the printed circuit board(or other installation surface for the module) at the time the solderballs are re-flowed to make the connection during installation of themodule. Such an arrangement can provide an additional path for heattransfer, and can additionally provide electrical connection of theshield to the installation board, as may be desired for someapplications. The supporting parts 305 and the lower planar part 304 ofthe heat spreader enclose the die 344, and can serve for protection fromambient and from mechanical stress to facilitate handling operationsand, particularly, during subsequent testing before the MPM assembly.

The top package 500 of multipackage module 82 is stacked over the bottompackage 300 upon a package attach region of the upper surface of thebottom package substrate and affixed there using an adhesive 503. Theadhesive 503 can be thermally conductive, to improve thermaldissipation.

The z-interconnection between the top package 500 and the bottom package300 according to the invention is made by wire bonds 818 between toppackage interconnect pads in the margin of the top package substrate 512and bottom package interconnect pads in the margin of the bottom packagesubstrate 342. The wire bonds may be formed in either up-bond ordown-bond (forward or reverse bonding) fashion. Parts of themultipackage module structure over the bottom package substrate areprotected by formation of a module encapsulant 807.

Solder balls 318 are reflowed onto exposed solder ball pads on the lowermetal layer of the bottom package substrate 300, for connection tounderlying circuitry, such as a printed circuit board (not shown in theFIGS.).

As will be appreciated from the foregoing, the structure according tothe invention allows for pre-testing of both the BGA and LGA beforeassembly into the multi-package module, to permit rejection ofnonconforming packages prior to assembly, and thereby to assure highfinal module test yields.

The processor chip in a flip chip bottom package according to thisaspect of the invention can be, for example, an ASIC, or a GPU, or aCPU, often an ASIC; and the top package can be, for example, a processorchip or, for example, a memory package or an ASIC package. Where the toppackage is a memory package it can be a stacked die memory package. Ashielded flip chip die-up bottom package can be particularly suitablefor higher speed applications, particularly for RF frequency processing,as in mobile communications applications.

Optionally, for improved heat dissipation from the multi-package module,a MPM having a flip chip bottom package in a die-up configuration (asshown for example in FIG. 8A or FIG. 8B) may be further provided with atop heat spreader over the top package in addition to the heatspreader/electrical shield on the bottom package as in FIG. 8B. Theoptional top heat spreader is formed of a thermally conductive materialhaving at least the more central area of its upper surface exposed atthe upper surface of the MPM to ambient for efficient heat exchange awayfrom the MPM. The top heat spreader may be, for example, a sheet ofmetal (such as copper or aluminum) or of any of a variety of otherthermally conductive materials, such as aluminum nitride. The heatspreader has a size and shape to substantially cover the package. Theheat spreader can be made thicker in a central area over the top packageto increase metal content, and thinner at the periphery so that it doesnot interfere with the z-interconnect wire bonds. If made thicker in acentral area the heat spreader may be affixed to the upward facingsurface of the top package. Or, a spacer may be placed over the upwardfacing surface of the package inboard of the wire bond sites, and theheat spreader may be affixed to the upper surface of the spacer.Alternately the heatspreader can be molded-in, resulting in a similarstructure but without the adhesive; that is, the heat spreader may bedropped into the MPM encapsulant mold and affixed at the upper surfaceof the module during the molding material curing process. Or, theheatspreader may have a generally planar portion over the top package,and a peripheral supporting portion or supporting members resting on ornear the upper surface of the bottom package substrate.

For example, a top heat spreader having a thicker central region can beaffixed to the upward facing surface of the top package as showndiagrammatically in a sectional view in FIG. 8C. The construction of thestacked packages in MPM 84 is generally similar to that of MPM 82 inFIG. 8B, and like structures are identified in the FIGS. by likereference numerals. The top heat spreader 530 in the example of FIG. 8Cis a generally planar piece of a thermally conductive material having atleast the more central area of its planar upper surface exposed toambient for efficient heat exchange away from the MPM. The top heatspreader 530 has a thicker central portion, inboard of the wire bondsites on the top package, and the thicker portion is affixed to theupward facing side 519 of the top package using an adhesive 532. Thethickness of the heat spreader may in some embodiments be in the range0.2 to 0.6 mm, nominally 0.4 mm. The top heat spreader may be, forexample, constructed of metal (such as copper, or aluminum). Where thetop heat spreader is made of copper, the lower surface is preferablytreated to have a black oxide, for improved adhesion to the attachmentmaterial beneath; the exposed upper surface may be treated to form ablack oxide, or it may be provided with a matte nickel (plate) surface.The adhesive 532 may optionally be a thermally conductive adhesive, suchas a thermally conductive epoxy, to provide improved heat dissipation;and the adhesive may be electrically nonconductive, in embodimentshaving exposed electrical features on the upward facing (“lower”) side.Usually the top heat spreader is affixed to the top package before themolding material is injected for the MPM encapsulation 807. Theperiphery of the top heat spreader may be encapsulated with the MPMmolding material. In the embodiment of FIG. 8C a step like re-entrantfeature 534 is provided on the periphery of the heat spreader 530 toallow for better mechanical integrity of the structure with lessdelamination from the molding compound.

As a further alternative, an MPM as in FIG. 8A or FIG. 8B can beprovided with a top heat spreader formed of a thermally conductivematerial having a generally planar central portion situated over the toppackage, and peripheral supporting members extending from near the edgesor the corners of the generally planar central portion to the uppersurface of the bottom package substrate 342, outside the z-interconnectbond pads and near the edge of bottom package. The upper surface of theplanar portion is exposed to ambient at the MPM upper surface forefficient heat exchange away from the MPM. The top heat spreader may beformed, for example, of a sheet of metal (such as copper), for exampleby stamping. The supporting members can optionally be affixed to theupper surface of the bottom package substrate using an adhesive. Theheat spreader supporting members are embedded in the MPM encapsulant 807during the molding material curing process. As in the embodiment of FIG.8B a step like re-entrant feature can be provided on the periphery ofthe planar upper portion of the heat spreader to allow for bettermechanical integrity of the structure with less delamination from themolding compound. In this embodiment the space between the lower surfaceof the planar central portion of the heat spreader and the upward facingsurface 519 of the top package is filled by a thin layer of the MPMmolding.

As a further alternative, an MPM as in FIG. 8A or FIG. 8B can beprovided with a simple planar heat spreader, with no supporting members,that is not attached to the upper surface of the top package molding. Insuch embodiments, as in the embodiment of FIG. 8B, the top heat spreadercan be a generally planar piece of a thermally conductive material suchas, for example, a sheet of metal (such as copper or aluminum), and atleast the more central area of the upper surface of the planar heatspreader is exposed to ambient for efficient heat exchange away from theMPM. Here, the heat spreader does not have a thicker central portioninboard of the wire bond sites on the upper package; instead, the spacebetween the lower surface of the simple planar heat spreader and theupward facing surface 519 of the top package may be filled by a thinlayer of the MPM molding, and such a simple planar heat spreader may beaffixed to the MPM encapsulant 807 during the molding material curingprocess. The periphery of such an unattached simple planar top heatspreader can be encapsulated with the MPM molding material, as in theattached planar heat spreader of FIG. 8B, and may be provided with astep-like re-entrant feature on the periphery to allow for bettermechanical integrity of the structure with less delamination from themolding compound.

An MPM structure having a heat spreader, as in FIG. 8C, or in thealternative embodiments described above, can provide significant thermalenhancement and may provide electrical shielding over the module, whichcan be critical to MPMs that combine RF and digital chips.

An advantage of a structure as in FIGS. 8B, 8C is significant thermalperformance and, optionally, electrical shielding at the bottom package,which can be particularly important critical, for example, in MPM thatcombine RF and digital chips. It is not necessary to have both a bottompackage heat spreader and a top heat spreader for all applications.Alternately one or the other may be adequate depending on the endproduct needs.

Inasmuch as no part of the upper surface of the bottom package substratein the die-up configuration is occupied by the bottom package die, aplurality of top packages can be stacked over a plurality of packageattach regions on the bottom package upper surface. This is illustratedby way of example in FIG. 8D. FIG. 8D is a diagrammatic sketch in asectional view thru an embodiment of a multipackage module generally at86, having a processor unit affixed to the lower surface of the bottompackage generally as shown in FIG. 8A (flip chip mounted in a “die-up”configuration), and a plurality of inverted LGA packages affixed to theupper side of the bottom package substrate according to an aspect of theinvention.

In the illustrative embodiment of FIG. 8D, a module substrate 816, also836, has a “lower” surface onto which solder balls 818 are attached, forconnection by solder reflow to, for example, a printed circuit board(not shown). A bottom package die 820 is mounted onto a die mountingportion of the lower surface of the module 816. As shown in thisexample, the processor 820 has a flip-chip configuration; it includes adie 824 electrically connected by way of balls or bumps 828 tointerconnect sites (not shown) in the lower surface of the modulesubstrate, and affixed to the surface using an adhesive underfillmaterial 825. A plurality of top packages 830, 830′ (there may typicallybe four memory packages; two are shown in the view of FIG. 8D) aremounted on the upper surface of the module substrate 836. In theembodiment illustrated in FIG. 8D the top packages are invertedsaw-singulated land grid array (LGA) packages. Referring particularly toLGA package 830, each LGA top package includes a die 834 affixed usingan adhesive to a top package substrate 835. The package substrate is, inthis example, a two-metal layer laminate, having patterned electricallyconductive traces on the upper and lower surfaces of a dielectric layer;selected upper and lower traces are connected by way of vias (not shown)through the dielectric layer. The downward-facing active surface of thedie is electrically connected to traces on the die attach “upper”(downward facing) surface of the top package substrate 835 by wire bonds832. The active surface of the die and the wire bonds are protected byan encapsulant 837. Further referring to FIG. 8D, the inverted toppackages 830, 830′ are affixed to the bottom package module substrate836 using an adhesive material 815, 815′ between the surface of theencapsulant 837 and the upper surface of the bottom package substrate836; and wire bonds 838 attached to wire bond pads on the upper surfaceof the top package substrate 835 provide for electrical connection towire bond pads in the upper surface of the bottom substrate 836.Additionally, passive devices, e.g., 819, can be affixed to andelectrically connected to traces in the upper surface of the bottompackage substrate 816. Also, in the illustrative example shown in FIG.8D, a heat spreader 814 is mounted onto the upper surface of the modulesubstrate and covers top packages 830, 830′; and the top packages andthe attachment arms of the heat spreader are encapsulated using anencapsulant material 817. A module such as is illustrated by way ofexample in FIG. 8D, where the processor is a GPU, for example, maytypically have a module footprint about 31 mm×31 mm and an overallprofile thickness about 2.8 mm or greater, with a 10.5 mm×10.5 mm GPUand 12 mm×12 mm memory BGA packages.

Multipackage modules configured as, for example in FIG. 8D, can beparticularly useful in applications where a large number of memory chipsare to be associated with a processor. The memory chips can be providedas top packages in this configuration, and the processor can be providedin the die-up flip chip bottom package. As may be appreciated, shieldingmay be provided around the bottom package die, as in FIG. 8B or 8C.

According to the invention, either the top package or the bottompackage, or both of them, in the multi-package module of the inventioncan include two or more stacked chips. FIGS. 9A and 9B illustrate, byway of example, embodiments of the invention 90, 92 in which each of thelower BGA package 490 and the inverted upper LGA package 590 has twostacked die. The stacked die in each package in this example arewire-bonded to their respective substrates, and adjacent die areseparated by a spacer, as is well known in the stacked-die package art.As will be appreciated, packages having other stacked dieconfigurations, including other die interconnects, can be used inmulti-package modules according to the invention, as well asside-by-side plural die arrangements. Referring particularly to FIG. 9A,the bottom package 490 has stacked die 492 and 494 separated by a spacer493; and the inverted top package 590 has stacked die 592 and 594separated by a spacer 593. The z-interconnection between the top andbottom packages is formed by wire bonds 598, connecting (in eitherforward- or reverse-bonding fashion) the upward-facing surfaces of thetop and bottom package substrates. The inverted top package 590 isaffixed onto the bottom package 490 using an adhesive 595. A moduleencapsulation 907 encloses parts of the module above the bottom packagesubstrate.

Stacked die packages are well established in the industry, with versionsthat have up to 5 stacked die in the package. The die have varioussizes, and the die in a stacked die package may have the same ordifferent relative sizes. The die are typically square or rectangular,and rectangular and square die of various dimensions may be stacked in astacked die package. Where the die are rectangular, or have variousdimensions, the die may be stacked so that the margin of a lower die inthe stack projects beyond the margin of an upper die that is stackedover it. FIGS. 9A and 9B show examples in which the two die in the stackare of the same size. In such embodiments, or in embodiments where anupper die in the stack is larger than a lower one, a spacer is assembledbetween the die to enable wire bonding of all the die to the LGAsubstrate.

For improved heat dissipation from the multi-package module havingstacked die in one or both of the top and the bottom package, a heatspreader may be provided over the top package. The top heat spreader isformed of a thermally conductive material having at least the morecentral area of its upper surface exposed at the upper surface of theMPM to ambient for efficient heat exchange away from the MPM. The topheat spreader may be, for example, a sheet of metal (such as copper oraluminum) or of any of a variety of other thermally conductivematerials, such as aluminum nitride. The heat spreader has a size andshape to substantially cover the package. The heat spreader can be madethicker in a central area over the top package to increase metalcontent, and thinner at the periphery so that it does not interfere withthe z-interconnect wire bonds. If made thicker in a central area theheat spreader may be affixed to the upward facing surface of the toppackage. Or, a spacer may be placed over the upward facing surface ofthe package inboard of the wire bond sites, and the heat spreader may beaffixed to the upper surface of the spacer. Alternately the heatspreadercan be molded-in, resulting in a similar structure but without theadhesive; that is, the heat spreader may be dropped into the MPMencapsulant mold and affixed at the upper surface of the module duringthe molding material curing process. Or, the heatspreader may have agenerally planar portion over the top package, and a peripheralsupporting portion or supporting members resting on or near the uppersurface of the bottom package substrate.

The module as shown for example in FIG. 9B is provided with a top heatspreader.

The top heat spreader 530 in the example of FIG. 9B is a generallyplanar piece of a thermally conductive material having at least the morecentral area of its planar upper surface exposed to ambient forefficient heat exchange away from the MPM. The top heat spreader 530 hasa thicker central portion, inboard of the wire bond sites on the toppackage, and the thicker portion is affixed to the upward facing side ofthe top package using an adhesive 532. The thickness of the heatspreader may in some embodiments be in the range 0.2 to 0.6 mm,nominally 0.4 mm. The top heat spreader may be, for example, constructedof metal (such as copper, or aluminum). Where the top heat spreader ismade of copper, the lower surface is preferably treated to have a blackoxide, for improved adhesion to the attachment material beneath; theexposed upper surface may be treated to form a black oxide, or it may beprovided with a matte nickel (plate) surface. The adhesive 532 mayoptionally be a thermally conductive adhesive, such as a thermallyconductive epoxy, to provide improved heat dissipation; and the adhesivemay be electrically nonconductive, in embodiments having exposedelectrical features on the upward facing (“lower”) side. Usually the topheat spreader is affixed to the top package before the molding materialis injected for the MPM encapsulation 907. The periphery of the top heatspreader may be encapsulated with the MPM molding material. In theembodiment of FIG. 9B a step like re-entrant feature 534 is provided onthe periphery of the heat spreader 530 to allow for better mechanicalintegrity of the structure with less delamination from the moldingcompound.

As a further alternative, an MPM as in FIG. 9A can be provided with atop heat spreader formed of a thermally conductive material having agenerally planar central portion situated over the top package, andperipheral supporting members extending from near the edges or thecorners of the generally planar central portion to the upper surface ofthe bottom package substrate, outside the z-interconnect bond pads andnear the edge of bottom package. The upper surface of the planar portionis exposed to ambient at the MPM upper surface for efficient heatexchange away from the MPM. The top heat spreader may be formed, forexample, of a sheet of metal (such as copper), for example by stamping.The supporting members can optionally be affixed to the upper surface ofthe bottom package substrate using an adhesive. The heat spreadersupporting members are embedded in the MPM encapsulant 907 during themolding material curing process. As in the embodiment of FIG. 9B a steplike re-entrant feature can be provided on the periphery of the planarupper portion of the heat spreader to allow for better mechanicalintegrity of the structure with less delamination from the moldingcompound. In this embodiment the space between the lower surface of theplanar central portion of the heat spreader and the upward facingsurface of the top package is filled by a thin layer of the MPM molding.

As a further alternative, an MPM as in FIG. 9A can be provided with asimple planar heat spreader, with no supporting members, that is notattached to the upper surface of the top package molding. In suchembodiments, as in the embodiment of FIG. 9B, the top heat spreader canbe a generally planar piece of a thermally conductive material such as,for example, a sheet of metal (such as copper or aluminum), and at leastthe more central area of the upper surface of the planar heat spreaderis exposed to ambient for efficient heat exchange away from the MPM.Here, the heat spreader does not have a thicker central portion inboardof the wire bond sites on the upper package; instead, the space betweenthe lower surface of the simple planar heat spreader and the uppersurface of the top package may be filled by a thin layer of the MPMmolding, and such a simple planar heat spreader may be affixed to theMPM encapsulant 907 during the molding material curing process. Theperiphery of such an unattached simple planar top heat spreader can beencapsulated with the MPM molding material, as in the attached planarheat spreader of FIG. 9B, and may be provided with a step-likere-entrant feature on the periphery to allow for better mechanicalintegrity of the structure with less delamination from the moldingcompound.

In some configurations the inverted top package can be constructedhaving a die on a substrate formed in the manner of a bump chip carrier(“BCC”). In a conventional BCC substrate, the die is affixed, using anadhesive, onto an upper surface of the leads, with the active surface ofthe die facing away from the leads. That is, the die is affixed with thepassive side toward the upper surface of the leads. The leads havecontact dents, formed convex on the lower side and concave on the upperside of the leads. The die is electrically connected by wire bondingfrom pads on the active side of the die to wire bonding sites in theconcavities. The bump convexities on the lower side of the leads providea standoff for direct interconnect of the BCC with an underlying printedcircuit, for example.

Conventionally the BCC leads are formed by deposition or plating on thesurface a blank having depressions situated where the dents are to belocated. Deposition or plating is done by a series of by masking anddeposition steps until the desired lead buildup is formed in the desiredshapes at the desired locations on the blank surface. Then the die isaffixed, passive side down, onto the upper surface of a die attachportion of the leadframe structure, using an adhesive; and the dieinterconnection is formed by wire bonding between wire bond pads on thedie and corresponding concave (upper) surfaces of the dents. A moldingstep is carried out, to encapsulate the die and wire bonds and to lendmechanical integrity to the assembly. Then the blank is stripped away,exposing the lower surfaces of the leads and of the convex surface ofthe bumps. Conventionally the BCC constructs are made in an array andare saw- or punch-singulated. At this point the BCC package is ready formounting.

BCC has been used primarily for RF or analog chips, which are small,that is from submillimeter to 5 mm size rectangular chips.

According to the invention, the inverted top package is constructed as aBCC type package, and the z-interconnect of the top package to thebottom package is made by way of wire bonding between wire bond sites onthe lower (upward facing) sides of the leads to wire bond sites on metallayer on the upper surface of the bottom package. Because the toppackage is inverted, and z-interconnect according to the invention ismade by wire bonding, no standoff from the lower side of the BCCsubstrate is required. That is, the “bumps” on the lower (upward facing)side of the BCC may be very low, and may be substantially flat. Also,according to the invention, the die interconnect wire bond sites on theupper surface of the leads and the z-interconnect sites on the lowersurface of the leads need not be at corresponding opposing positions,although it may be advantageous for them to be so situated.

The BCC substrate for the top package according to the invention isbuilt up by serial deposition or plating of thin metal layers,preferably layers of Pd, Ni, Pd, and Au (Pd/Ni/Pd/Au), nominally forexample of thicknesses 0.5 μm/5 μm/<0.1 μm, respectively. For wirebonding interconnect, a gold (preferred) or aluminum or silver finish isemployed on the wire bond pad surfaces. The substrate is very thin,having a thickness typically in the range 7 μm to 10 μm. Additionally,the bumps can be made very small on BCC substrates, typically about 75μm. Die can be stacked over the BCC following established stackingtechniques employing laminate or tape substrates.

FIGS. 10A and 10B show examples of multipackage modules, generally at100 and at 102, respectively, having inverted BCC top packages 1000,1020, respectively, stacked over BCC bottom packages 1400 according tothe invention. The BCC bottom packages in these examples are BGApackages substantially similar to the BGA bottom package as shown inFIG. 5A, for example, and the various parts, readily identifiable byreference to FIG. 5A, are not separately renumbered in FIGS. 10A and10B. The top BCC type package 1000 in FIG. 10A includes a die 1002affixed using an adhesive 1003 to an “upper” surface of a die attachportion 1004 of a built-up lead frame structure additionally havinginterconnect leads 1006. The die is interconnected by wire bonds 1005connecting pads on the active side of the die with the “upper” surfaceof corresponding leads 1006. As noted above, the BCC according to theinvention may be a standard BCC, having standoff bumps on the leads; or,because there is no need for standoff, the leads may be substantiallyflat, as may be preferred. The die 1002, the wire bonds 1005, and theexposed upper surfaces of the leads 1006 are protected by anencapsulation 1007. The top packages 1000 may be made in array fashion,and saw- or punch-singulated to provide separate top packages forsubsequent processing.

The completed top package 1000, 1020 is inverted and affixed upper sidedownward upon an upper surface of a prepared (and tested) BGA bottompackage 1400, using an adhesive 1008. The z-interconnect between the topand bottom packages is made by wire bonds (forward or reverse) 1010between the “lower” (upward-facing) surfaces of the leads 1006 and theupper surfaces of wire bond attach sites on the upper metal layer of theBGA substrate. Solder balls are affixed to the lower surface of thebottom package substrate for attachment of the package to, for example,a printed circuit board for installation in a device. The structuresabove the bottom package substrate are covered by an encapsulation 1012,and the package is saw- or punch-singulated.

In FIG. 10B, the top package 1020 has an additional die 1022 stacked onthe “upper” (downward facing) side of the die 1002 that is directlymounted on the BCC substrate. The additional die 1022 is interconnectedto the leads by wire bonds 1025 between wire bond pads in the die andwire bond sites on the upper surface of the leads. In this example, aspacer 1021 is employed between the BCC die and the additional die toprovide clearance for the loops of the wire bonds 1005.

In other configurations according to the invention, an additional chipmay be attached to the bottom (upward) side of the inverted top package,using either a flip chip interconnect (as shown for example generally at110 in FIG. 11A) or wire bond interconnect (as shown for examplegenerally at 112 in FIG. 11B) to produce an MPM having increasedfunctionality. In FIG. 11A the additional die 1102 is connected to siteson the top package 1104 upward facing surface by clip chipinterconnections 1103. In FIG. 11B the additional die 1112 is affixed tothe top package 1114 upward facing surface using an adhesive 1115, andthe interconnection is made by wire bonds 1113 between wire bond pads(not shown) on the active surface of the additional die 1112 and wirebond sites on the top package 1114 “lower” (upward-facing) metal layer.

In still other configurations according to the invention, an additionalpackage is attached on the upward facing surface of the inverted toppackage. The additional package can also be an inverted LGA, as appearsfor example generally at 114 in FIG. 11C, and the z-interconnection ofthe additional LGA 1142 and the inverted LGA 1144 to which it isattached can be made by wire bonding 1143. Or, the additional packagecan be upside upward, as appears for example generally at 116 in FIG.11D, and the z-interconnection of the additional BGA 1162 to theinverted LGA 1164 beneath can be made by solder ball interconnection byway of reflowed solder balls 1163.

As will be appreciated, in all its various aspects the inventionfeatures a lower BGA package and an inverted upper LGA package stackedover the lower BGA package, and the invention features wire bonding asthe z-interconnect method between stacked packages.

The multi-package module according to the invention can be used forbuilding computers, and, for example, in telecommunications, consumerand industrial electronics devices. The invention provides for assemblyof more than one semiconductor in a thin and minimal footprint packageat high final test yields. Construction of the individual packagesallows testing before they are assembled into the MPM, assuring thatonly acceptably good package components are employed in MPM assemblyand, accordingly, ensuring high MPM assembly yields.

The invention provides for flexibility in module design, particularly ininterconnect configuration, and enables the use of standard packages,reducing the need for custom design and reducing cost. The invertedupper package in the module is assembled using either of the two mostcommon methods of singulation, namely saw or punch singulation. Thelower package is cavity molded to expose the bond fingers forz-interconnect.

Attaching the upper package upside down over the lower package bringsthe bottom side upward in the inverted upper package and thereby leavesthe bottom side exposed. This allows wire bonding directly from theupward surface of the inverted mold array saw singulated upper packagesto the bottom package. Moreover, a heatspreader can be attached to theexposed bottom (upward) side of the upper package, to increase powerdissipation of the MPM to ambient by way of the upward surface of theheatspreader.

Additionally, exposing the bottom side of the upper package permitsattachment of and electrical connection of an additional die or of anadditional package, to the bottom side of the top package to furtherincrease functionality in the same footprint.

Because according to the invention the z-interconnect between theinverted upper package and the lower package is by otherwiseconventional wire bonding, providing advantages in stacking of standardpackages, established manufacturing infrastructure, low cost, designflexibility and thin package.

Generally, the LGAs stacked on a lower BGA must be smaller (in the x-yplane) than the BGA to allow space at the periphery for the wire bonds.The wire diameter typically is of the order of 0.025 mm (0.050 to 0.010mm range). The wire distance to the LGA substrate edge can differ invarious embodiments, but is no less than a wire diameter. The relativesizes of BGA and LGA are determined primarily by the maximum die size ineach. The die thickness and mold cap thickness primarily determine howmany die can be stacked in one package.

Procedures in processes for making BGA packages and LGA packages for usein the invention are well established in the industry for both the wirebonded and the flip chip types of packages.

Testing of BGAs is well established in the industry, and typically isdone by accessing contact to the solder ball pads. The LGAs can betested in either of two ways, namely by accessing the LGA pads on thelower surface of the LGA of the substrate, similar to the pads of thesolder balls in a BGA; or by accessing the z-interconnect pads on theupper surface of the substrate. The completed MPM assembly can be testedin the same as for testing BGAs.

The MPM assembly process is similar for the configurations according tothe various aspects of the invention. Generally, the process includessteps of providing a first molded package including a first packagesubstrate and at least one die attached to the first package substrate,dispensing adhesive onto an upper surface of the first molded package,placing a second molded package including a second package substrate andat least one die such that a lower surface of the second substratecontacts the adhesive on the upper surface of the first package, duringthe adhesive, and forming z-interconnects between the first and secondsubstrate. Advantageously, the packages can be tested prior to assembly,and package is not meeting requirements for performance or reliabilitycan be discarded, so that first packages and second package is tested as“good” are used in the assembled module.

FIG. 12 is a flow diagram showing a process for assembly of amulti-package module as shown for example in FIG. 5A. In a step 1202, anunsingulated strip of ball grid array packages is provided. The die andwire bond structures on the ball grid array packages are protected by amolding. The BGA packages in the strip preferably are tested (asindicated in the FIG. by *) for performance and reliability before theyare taken to subsequent steps in the process. Only packages identifiedas “good” are subjected to subsequent treatment. In a step 1204,adhesive is dispensed over the upper surface of the molding on “good”BGA packages. In a step 1206, singulated land grid array packages areprovided. The singulated LGA packages are protected by a molding, andpreferably are tested (*) and identified as “good”. In a step 1208, apick-and-place operation is carried out to invert and place “good” LGApackages on the adhesive over the molding on the “good” BGA packages. Ina step 1210, the adhesive is cured. In a step 1212, a plasma cleanoperation is performed in preparation for a step 1214 in which wire bondz-interconnections are formed between the stacked top LGA and bottom BGApackages. In a step 1216, an additional plasma clean may be performed,followed by the formation of the MPM molding in a step 1218. In a step1220, the second-level interconnect solder balls are attached to theunderside of the module. In a step 1222, the completed modules aretested (*) and singulated from the strip, for example by saw singulationor by punch singulation, and packaged for further use.

FIG. 13 is a flow diagram showing a process for assembly of amulti-package module according to the invention, in which the bottompackage is provided with a heat shield/heat spreader. In a step 1402, anunsingulated strip of ball grid array packages is provided. The BGApackages have shields affixed over the die. The shields protect the dieand wire bond structures on the ball grid array packages, andaccordingly no package molding is required. The BGA packages in thestrip preferably are tested (as indicated in the FIG. by *) forperformance and reliability before they are taken to subsequent steps inthe process. Only packages identified as “good” are subjected tosubsequent treatment. In a step 1404, adhesive is dispensed over theupper surface of the shields on “good” BGA packages. In a step 1406,singulated land grid array packages are provided. The singulated LGApackages are protected by a molding, and preferably are tested (*) andidentified as “good”. In a step 1408, a pick-and-place operation iscarried out to invert and place “good” LGA packages on the adhesive overthe shields on the “good” BGA packages. In a step 1410, the adhesive iscured. In a step 1412, a plasma clean operation is performed inpreparation for a step 1414 in which wire bond z-interconnections areformed between the stacked top LGA and bottom BGA packages. In a step1416, an additional plasma clean may be performed, followed by theformation of the MPM molding in a step 1418. In a step 1420, a deflashoperation may be carried out, to decompose and remove undesirableorganic material. The deflash may be carried out by laser, or bychemical or plasma clean. In a step 1422, the second-level interconnectsolder balls are attached to the underside of the module. In a step1424, the completed modules are tested (*) and singulated from thestrip, for example by saw singulation or by punch singulation, andpackaged for further use.

FIG. 14 is a flow diagram showing a process for assembly of amulti-package module, in which the bottom package is provided with aheat shield/heat spreader, and the module is further provided with a topheat spreader. This process is similar to the one shown in FIG. 13, withadditional steps interposed for installation of the heat spreader by a“drop-in” mold operation. Like steps in the process are identified bylike reference numerals in the FIGS. In a step 1402, an unsingulatedstrip of ball grid array packages is provided. The BGA packages haveshields affixed over the die. The shields protect the die and wire bondstructures on the ball grid array packages, and accordingly no packagemolding is required. The BGA packages in the strip preferably are tested(as indicated in the FIG. by *) for performance and reliability beforethey are taken to subsequent steps in the process. Only packagesidentified as “good” are subjected to subsequent treatment. In a step1404, adhesive is dispensed over the upper surface of the shields on“good” BGA packages. In a step 1406, singulated land grid array packagesare provided. The singulated LGA packages are protected by a molding,and preferably are tested (*) and identified as “good”. In a step 1408,a pick-and-place operation is carried out to invert and place “good” LGApackages on the adhesive over the shields on the “good” BGA packages. Ina step 1410, the adhesive is cured. In a step 1412, a plasma cleanoperation is performed in preparation for a step 1414 in which wire bondz-interconnections are formed between the stacked top LGA and bottom BGApackages. In a step 1416, an additional plasma clean may be performed.In a step 1415, a heat spreader is dropped into each mold cavity in acavity molding apparatus. In a step 1417, a clean package stack fromstep 1416 is dropped into the mold cavity over the heat spreader. In astep 1419, an encapsulation material is injected into the mold cavity,and cured to form the MPM molding. In a step 1421, a deflash operationmay be carried out, to decompose and remove undesirable organicmaterial. The deflash may be carried out by laser, or by chemical orplasma clean. In a step 1422, the second-level interconnect solder ballsare attached to the underside of the module. In a step 1424, thecompleted modules are tested (*) and singulated from the strip, forexample by saw singulation or by punch singulation, and packaged forfurther use.

FIG. 15 is a flow diagram showing a process for assembly of amulti-package module in which the bottom package is a flip chip packagein a die-down configuration. In a step 1502, an unsingulated strip ofdie-down flip chip ball grid array bottom packages is provided. The BGApackages may or may not be provided with molding, and are providedwithout second-level interconnect solder balls. The BGA packages in thestrip preferably are tested (as indicated in the FIG. by *) forperformance and reliability before they are taken to subsequent steps inthe process. Only packages identified as “good” are subjected tosubsequent treatment. In a step 1504, adhesive is dispensed onto theupper surface (back side) of the die on “good” BGA packages. In a step1506, singulated land grid array packages are provided. The singulatedLGA packages are protected by a molding, and preferably are tested (*)and identified as “good”. In a step 1508, a pick-and-place operation iscarried out to invert and place “good” LGA packages on the adhesive overthe die on the “good” BGA packages. In a step 1510, the adhesive iscured. In a step 1512, a plasma clean operation is performed inpreparation for a step 1514 in which wire bond z-interconnections areformed between the stacked top LGA and bottom BGA packages. In a step1516, an additional plasma clean may be performed, followed by theformation of the MPM molding in a step 1518. In a step 1520, thesecond-level interconnect solder balls are attached to the underside ofthe module. In a step 1522, the completed modules are tested (*) andsingulated from the strip, for example by saw singulation or by punchsingulation, and packaged for further use.

FIG. 16 is a flow diagram showing a process for assembly of amulti-package module in which the bottom package is a flip chip packagein a die-down configuration, and in which the module os further providedwith a heat shield. This process is similar to the one shown in FIG. 15,with an additional step interposed for installation of the shield overthe bottom package flip chip die. Like steps in the process areidentified by like reference numerals in the FIGS. In a step 1602, anunsingulated strip of die-down flip chip ball grid array bottom packagesis provided. The BGA packages may or may not be provided with molding,and are provided without second-level interconnect solder balls. The BGApackages in the strip preferably are tested (as indicated in the FIG. by*) for performance and reliability before they are taken to subsequentsteps in the process. Only packages identified as “good” are subjectedto subsequent treatment. In a step 1603, the electrical shield isaffixed over the die on “good” bottom BGA packages. In a step 1604,adhesive is dispensed onto the upper surface of the shield on “good” BGApackages. In a step 1606, singulated land grid array packages areprovided. The singulated LGA packages are protected by a molding, andpreferably are tested (*) and identified as “good”. In a step 1608, apick-and-place operation is carried out to invert and place “good” LGApackages on the adhesive over the shields on the “good” BGA packages. Ina step 1610, the adhesive is cured. In a step 1612, a plasma cleanoperation is performed in preparation for a step 1614 in which wire bondz-interconnections are formed between the stacked top LGA and bottom BGApackages. In a step 1616, an additional plasma clean may be performed,followed by the formation of the MPM molding in a step 1618. In a step1620, the second-level interconnect solder balls are attached to theunderside of the module. In a step 1622, the completed modules aretested (*) and singulated from the strip, for example by saw singulationor by punch singulation, and packaged for further use.

FIG. 17 is a flow diagram showing a process for assembly of amulti-package module in which the bottom package is a flip chip packagein a die-up configuration. In a step 1702, an unsingulated strip ofdie-up flip chip ball grid array packages is provided. The flip chipinterconnects are protected by an underfill or molding between the dieand the die attach surface of the bottom substrate, and so noovermolding is required. The BGA packages in the strip preferably aretested (as indicated in the FIG. by *) for performance and reliabilitybefore they are taken to subsequent steps in the process. Only packagesidentified as “good” are subjected to subsequent treatment. In a step1704, adhesive is dispensed over the upper surface of the substrate on“good” BGA packages. In a step 1706, singulated second packages areprovided, which may be stacked die packages, as for example in FIGS. 10Aand 10B. The singulated second packages are protected by a molding, andpreferably are tested (*) and identified as “good”. In a step 1708, apick-and-place operation is carried out to invert and place “good”second packages on the adhesive over the substrate on the “good” BGApackages. In a step 1710, the adhesive is cured. In a step 1712, aplasma clean operation is performed in preparation for a step 1714 inwhich wire bond z-interconnections are formed between the stacked top(stacked die) and bottom die-up flip chip BGA packages. In a step 1716,an additional plasma clean may be performed, followed by the formationof the MPM molding in a step 1718. In a step 1720, the second-levelinterconnect solder balls are attached to the underside of the module.In a step 1722, the completed modules are tested (*) and singulated fromthe strip, for example by saw singulation or by punch singulation, andpackaged for further use.

FIG. 18 is a flow diagram showing a process for assembly of amulti-package module in which the top and bottom package are stacked diepackages. In a step 1802, an unsingulated strip of stacked die ball gridarray packages is provided. The stacked die BGA packages are molded,providing an upper package surface. The BGA packages in the strippreferably are tested (as indicated in the FIG. by *) for performanceand reliability before they are taken to subsequent steps in theprocess. Only packages identified as “good” are subjected to subsequenttreatment. In a step 1804, adhesive is dispensed over the upper surfaceof the substrate on “good” stacked die BGA packages. In a step 1806,singulated second packages are provided, which may be stacked diepackages, as for example in FIG. 11. The singulated second packages areprotected by a molding, and preferably are tested (*) and identified as“good”. In a step 1808, a pick-and-place operation is carried out toinvert and place “good” second packages on the adhesive over thesubstrate on the “good” BGA packages. In a step 1810, the adhesive iscured. In a step 1812, a plasma clean operation is performed inpreparation for a step 1814 in which wire bond z-interconnections areformed between the stacked top (stacked die) and bottom die-up flip chipBGA packages. In a step 1816, an additional plasma clean may beperformed, followed by the formation of the MPM molding in a step 1818.In a step 1820, the second-level interconnect solder balls are attachedto the underside of the module. In a step 1822, the completed modulesare tested (*) and singulated from the strip, for example by sawsingulation or by punch singulation, and packaged for further use.

As will be appreciated, individual ones of the various steps in theprocesses according to the invention can be carried out, according tothe methods described herein, using substantially conventionaltechniques, with straightforward modification, as described herein, ofconventional fabrication facilities. Such variation of conventionaltechniques and modification of conventional fabrication apparatus as maybe required can be accomplished using the description herein withoutundue experimentation.

Other embodiments are within the following claims.

1. A method for making a multipackage module, comprising: providing aBGA first package comprising a first package substrate; providing asecond package comprising a second package substrate; inverting thesecond package and stacking the inverted second package over the firstpackage; and electrically interconnecting the first and second packageby wire bonds, each wire bond extending outwardly from the secondpackage and connecting the first and second substrates.
 2. The method ofclaim 1, said BGA first package being a molded package, the moldinghaving a generally planar upper surface, wherein stacking the invertedsecond package over the first package comprises applying an adhesiveonto the molding upper surface and placing the inverted second packageonto the adhesive.
 3. The method of claim 2 wherein the adhesive is acurable adhesive, and further comprising curing the adhesive.
 4. Themethod of claim 1 wherein providing the BGA first package comprisesproviding an unsingulated strip of BGA packages.
 5. The method of claim1 where providing the BGA first package comprises testing BGA packagesfor a performance and reliability requirement and identifying the saidfirst package as meeting the requirement.
 6. The method of claim 1 whereproviding the second package comprises testing packages for aperformance and reliability requirement and identifying the said secondpackage as meeting the requirement.
 7. The method of claim 1, furthercomprising attaching second-level interconnect balls onto the BGA firstpackage substrate.
 8. The method of claim 1, further comprisingencapsulating the stacked packages in a multipackage module molding. 9.The method of claim 1, further comprising singulating the modules. 10.The method of claim 1 wherein providing the second package comprisesproviding a land grid array package.
 11. The method of claim 1 whereinproviding the second package comprises providing a land grid arraypackage, the land grid array package being at least partially molded.12. The method of claim 11, the land grid array package being fullymolded.
 13. The method of claim 11, the wire bonds of the land gridarray package being molded, and at least a portion of an upward facingsurface of an upper die being exposed.
 14. The method of claim 1 whereinthe BGA first package is provided with an electromagnetic shield affixedover the die.
 15. The method of claim 14, the shield having a generallyplanar upper surface, wherein stacking the inverted second package overthe first package comprises applying an adhesive onto the shield uppersurface and placing the inverted second package onto the adhesive. 16.The method of claim 15 wherein the adhesive is a curable adhesive, andfurther comprising curing the adhesive.
 17. The method of claim 1,further comprising providing a heat spreader.
 18. The method of claim17, wherein providing a heat spreader comprises carrying out a drop-inmold operation, the heat spreader being placed into a mold prior toforming a module molding.
 19. The method of claim 17, wherein providinga heat spreader comprises affixing a generally planar portion of a heatspreader onto a generally planar upward facing surface of the invertedsecond package.